refactor: remove file token feature

Problem: The file metadata token (file:<path>:<line>) was implemented
but is no longer wanted.

Solution: Remove all traces — parse.lua token parsing, diff.lua
reconciliation, views.lua LineMeta field, buffer.lua virtual text and
PendingFile highlight, complete.lua omnifunc trigger, init.lua
goto_file/add_here functions and -file edit token, plugin keymaps
<Plug>(pending-goto-file) and <Plug>(pending-add-here), config.lua
goto_file keymap field, vimdoc FILE TOKEN section, and
spec/file_spec.lua.

lua/pending/init.lua

@@ -324,15 +324,6 @@ function M._setup_buf_mappings(bufnr)
     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
@@ -664,10 +655,6 @@ 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
     local resolved = parse.resolve_date(due_val)
@@ -711,11 +698,10 @@ local function parse_edit_token(token)
       .. dk
       .. ':<date>, cat:<name>, '
       .. rk
-      .. ':<pattern>, file:<path>:<line>, +!, -!, -'
+      .. ':<pattern>, +!, -!, -'
       .. dk
       .. ', -cat, -'
       .. rk
-      .. ', -file'
 end
 
 ---@param id_str string
@@ -795,9 +781,6 @@ 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
 
@@ -810,17 +793,6 @@ function M.edit(id_str, rest)
 
   s:update(id, updates)
 
-  if updates.file_clear then
-    local t = s: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
-
   s:save()
 
   local bufnr = buffer.bufnr()
@@ -831,91 +803,6 @@ 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 = get_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(get_store().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 s = get_store()
-  local data_dir = vim.fn.fnamemodify(s.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
-  s:load()
-  local tasks = s: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]]
-    s:save()
-    vim.notify('Attached ' .. file_spec .. ' to task ' .. task.id)
-  end)
-end
-
 ---@return nil
 function M.init()
   local path = vim.fn.getcwd() .. '/.pending.json'