feat(file-token): add file: inline metadata token with gf navigation

Problem: there was no way to link a task to a specific location in a
source file, or to quickly jump from a task to the relevant code.

Solution: add a file:<path>:<line> inline token that stores a relative
file reference in task._extra.file. Virtual text renders basename:line
in a new PendingFile highlight group. A buffer-local gf mapping
(configurable via keymaps.goto_file) opens the file at the given line.
M.add_here() lets users attach the current cursor position to any task
via vim.ui.select(). M.edit() gains -file support to clear the
reference. <Plug>(pending-goto-file) and <Plug>(pending-add-here) are
exposed for custom mappings.

lua/pending/buffer.lua

@@ -136,6 +136,10 @@ local function apply_extmarks(bufnr, line_meta)
       if m.due then
         table.insert(virt_parts, { m.due, due_hl })
       end
+      if m.file then
+        local display = m.file:match('([^/]+:%d+)$') or m.file
+        table.insert(virt_parts, { display, 'PendingFile' })
+      end
       if #virt_parts > 0 then
         for p = 1, #virt_parts - 1 do
           virt_parts[p][1] = virt_parts[p][1] .. '  '
@@ -170,6 +174,7 @@ local function setup_highlights()
   vim.api.nvim_set_hl(0, 'PendingDone', { link = 'Comment', default = true })
   vim.api.nvim_set_hl(0, 'PendingPriority', { link = 'DiagnosticWarn', default = true })
   vim.api.nvim_set_hl(0, 'PendingRecur', { link = 'DiagnosticInfo', default = true })
+  vim.api.nvim_set_hl(0, 'PendingFile', { link = 'Directory', default = true })
 end
 
 local function snapshot_folds(bufnr)

lua/pending/complete.lua

@@ -121,6 +121,7 @@ function M.omnifunc(findstart, base)
       { vim.pesc(dk) .. ':([%S]*)$', dk },
       { 'cat:([%S]*)$', 'cat' },
       { vim.pesc(rk) .. ':([%S]*)$', rk },
+      { 'file:([%S]*)$', 'file' },
     }
 
     for _, check in ipairs(checks) do
@@ -162,6 +163,7 @@ function M.omnifunc(findstart, base)
         table.insert(matches, { word = c.word, menu = '[' .. source .. ']', info = c.info })
       end
     end
+  elseif source == 'file' then
   end
 
   return matches

lua/pending/config.lua

@@ -22,6 +22,7 @@
 ---@field prev_header? string|false
 ---@field next_task? string|false
 ---@field prev_task? string|false
+---@field goto_file? string|false
 
 ---@class pending.Config
 ---@field data_path string

lua/pending/diff.lua

@@ -12,6 +12,7 @@ local store = require('pending.store')
 ---@field due? string
 ---@field rec? string
 ---@field rec_mode? string
+---@field file? string
 ---@field lnum integer
 
 ---@class pending.diff
@@ -52,6 +53,7 @@ function M.parse_buffer(lines)
           due = metadata.due,
           rec = metadata.rec,
           rec_mode = metadata.rec_mode,
+          file = metadata.file,
           lnum = i,
         })
       end
@@ -65,8 +67,9 @@ function M.parse_buffer(lines)
 end
 
 ---@param lines string[]
+---@param hidden_ids? table<integer, boolean>
 ---@return nil
-function M.apply(lines)
+function M.apply(lines, hidden_ids)
   local parsed = M.parse_buffer(lines)
   local now = timestamp()
   local data = store.data()
@@ -127,6 +130,19 @@ function M.apply(lines)
           task.recur_mode = entry.rec_mode
           changed = true
         end
+        local old_file = (task._extra and task._extra.file) or nil
+        if entry.file ~= old_file then
+          task._extra = task._extra or {}
+          if entry.file then
+            task._extra.file = entry.file
+          else
+            task._extra.file = nil
+            if next(task._extra) == nil then
+              task._extra = nil
+            end
+          end
+          changed = true
+        end
         if entry.status and task.status ~= entry.status then
           task.status = entry.status
           if entry.status == 'done' then

lua/pending/init.lua

@@ -1,4 +1,5 @@
 local buffer = require('pending.buffer')
+local config = require('pending.config')
 local diff = require('pending.diff')
 local parse = require('pending.parse')
 local store = require('pending.store')
@@ -240,6 +241,16 @@ function M._setup_buf_mappings(bufnr)
       end, opts)
     end
   end
+
+  local goto_key = km.goto_file
+  if goto_key == nil then
+    goto_key = 'gf'
+  end
+  if goto_key and goto_key ~= false then
+    vim.keymap.set('n', goto_key --[[@as string]], function()
+      M.goto_file()
+    end, opts)
+  end
 end
 
 ---@param bufnr integer
@@ -550,6 +561,9 @@ local function parse_edit_token(token)
   if token == '-rec' or token == '-' .. rk then
     return 'recur', vim.NIL, nil
   end
+  if token == '-file' then
+    return 'file_clear', true, nil
+  end
 
   local due_val = token:match('^' .. vim.pesc(dk) .. ':(.+)$')
   if due_val then
@@ -594,10 +608,11 @@ local function parse_edit_token(token)
       .. dk
       .. ':<date>, cat:<name>, '
       .. rk
-      .. ':<pattern>, +!, -!, -'
+      .. ':<pattern>, file:<path>:<line>, +!, -!, -'
       .. dk
       .. ', -cat, -'
       .. rk
+      .. ', -file'
 end
 
 ---@param id_str string
@@ -676,6 +691,9 @@ function M.edit(id_str, rest)
     elseif field == 'priority' then
       updates.priority = value
       table.insert(feedback, value == 1 and 'priority added' or 'priority removed')
+    elseif field == 'file_clear' then
+      updates.file_clear = true
+      table.insert(feedback, 'file reference removed')
     end
   end
 
@@ -687,6 +705,18 @@ function M.edit(id_str, rest)
   end
 
   store.update(id, updates)
+
+  if updates.file_clear then
+    local t = store.get(id)
+    if t and t._extra then
+      t._extra.file = nil
+      if next(t._extra) == nil then
+        t._extra = nil
+      end
+      t.modified = os.date('!%Y-%m-%dT%H:%M:%SZ') --[[@as string]]
+    end
+  end
+
   store.save()
 
   local bufnr = buffer.bufnr()
@@ -697,6 +727,90 @@ function M.edit(id_str, rest)
   vim.notify('Task #' .. id .. ' updated: ' .. table.concat(feedback, ', '))
 end
 
+---@return nil
+function M.goto_file()
+  local bufnr = vim.api.nvim_get_current_buf()
+  if vim.bo[bufnr].filetype ~= 'pending' then
+    return
+  end
+  local lnum = vim.api.nvim_win_get_cursor(0)[1]
+  local meta = buffer.meta()
+  local m = meta and meta[lnum]
+  if not m or m.type ~= 'task' then
+    vim.notify('No task on this line', vim.log.levels.WARN)
+    return
+  end
+  local task = store.get(m.id)
+  if not task or not task._extra or not task._extra.file then
+    vim.notify('No file attached to this task', vim.log.levels.WARN)
+    return
+  end
+  local file_spec = task._extra.file
+  local rel_path, line_str = file_spec:match('^(.+):(%d+)$')
+  if not rel_path then
+    vim.notify('Invalid file spec: ' .. file_spec, vim.log.levels.ERROR)
+    return
+  end
+  local data_dir = vim.fn.fnamemodify(config.get().data_path, ':h')
+  local abs_path = data_dir .. '/' .. rel_path
+  if vim.fn.filereadable(abs_path) == 0 then
+    vim.notify('File not found: ' .. abs_path, vim.log.levels.ERROR)
+    return
+  end
+  vim.cmd.edit(abs_path)
+  local lnum_target = tonumber(line_str) or 1
+  vim.api.nvim_win_set_cursor(0, { lnum_target, 0 })
+end
+
+---@return nil
+function M.add_here()
+  local cur_bufnr = vim.api.nvim_get_current_buf()
+  if vim.bo[cur_bufnr].filetype == 'pending' then
+    vim.notify('Already in pending buffer', vim.log.levels.WARN)
+    return
+  end
+  local cur_file = vim.api.nvim_buf_get_name(cur_bufnr)
+  if cur_file == '' or vim.fn.filereadable(cur_file) == 0 then
+    vim.notify('Not editing a readable file', vim.log.levels.ERROR)
+    return
+  end
+  local cur_lnum = vim.api.nvim_win_get_cursor(0)[1]
+  local data_dir = vim.fn.fnamemodify(config.get().data_path, ':h')
+  local abs_file = vim.fn.fnamemodify(cur_file, ':p')
+  local rel_file
+  if abs_file:sub(1, #data_dir + 1) == data_dir .. '/' then
+    rel_file = abs_file:sub(#data_dir + 2)
+  else
+    rel_file = abs_file
+  end
+  local file_spec = rel_file .. ':' .. cur_lnum
+  store.load()
+  local tasks = store.active_tasks()
+  if #tasks == 0 then
+    vim.notify('No active tasks', vim.log.levels.INFO)
+    return
+  end
+  local items = {}
+  for _, task in ipairs(tasks) do
+    table.insert(items, task)
+  end
+  vim.ui.select(items, {
+    prompt = 'Attach file to task:',
+    format_item = function(task)
+      return '[' .. task.id .. '] ' .. task.description
+    end,
+  }, function(task)
+    if not task then
+      return
+    end
+    task._extra = task._extra or {}
+    task._extra.file = file_spec
+    task.modified = os.date('!%Y-%m-%dT%H:%M:%SZ') --[[@as string]]
+    store.save()
+    vim.notify('Attached ' .. file_spec .. ' to task ' .. task.id)
+  end)
+end
+
 ---@param args string
 ---@return nil
 function M.command(args)

lua/pending/parse.lua

@@ -416,7 +416,7 @@ end
 
 ---@param text string
 ---@return string description
----@return { due?: string, cat?: string, rec?: string, rec_mode?: 'scheduled'|'completion' } metadata
+---@return { due?: string, cat?: string, rec?: string, rec_mode?: 'scheduled'|'completion', file?: string } metadata
 function M.body(text)
   local tokens = {}
   for token in text:gmatch('%S+') do
@@ -481,7 +481,18 @@ function M.body(text)
             metadata.rec = raw_spec
             i = i - 1
           else
-            break
+            local file_path_val, file_line_val = token:match('^file:(.+):(%d+)$')
+            if file_path_val and file_line_val then
+              if metadata.file then
+                break
+              end
+              metadata.file = file_path_val .. ':' .. file_line_val
+              i = i - 1
+            elseif token:match('^file:') then
+              break
+            else
+              break
+            end
           end
         end
       end
@@ -499,7 +510,7 @@ end
 
 ---@param text string
 ---@return string description
----@return { due?: string, cat?: string, rec?: string, rec_mode?: 'scheduled'|'completion' } metadata
+---@return { due?: string, cat?: string, rec?: string, rec_mode?: 'scheduled'|'completion', file?: string } metadata
 function M.command_add(text)
   local cat_prefix = text:match('^(%S.-):%s')
   if cat_prefix then

lua/pending/views.lua

@@ -12,6 +12,7 @@ local parse = require('pending.parse')
 ---@field show_category? boolean
 ---@field priority? integer
 ---@field recur? string
+---@field file? string
 
 ---@class pending.views
 local M = {}
@@ -159,6 +160,7 @@ function M.category_view(tasks)
         overdue = task.status == 'pending' and task.due ~= nil and parse.is_overdue(task.due)
           or nil,
         recur = task.recur,
+        file = task._extra and task._extra.file or nil,
       })
     end
   end
@@ -210,6 +212,7 @@ function M.priority_view(tasks)
       overdue = task.status == 'pending' and task.due ~= nil and parse.is_overdue(task.due) or nil,
       show_category = true,
       recur = task.recur,
+      file = task._extra and task._extra.file or nil,
     })
   end