feat(buffer): render forge links as inline conceal overlays

Problem: forge tokens were stripped from the buffer and shown as EOL
virtual text via `%l`. The token disappeared from the editable line,
and multi-ref tasks broke.

Solution: compute `forge_spans` in `views.lua` with byte offsets for
each forge token in the rendered line. In `apply_inline_row()`, place
extmarks with `conceal=''` and `virt_text_pos='inline'` to visually
replace each raw token with its formatted label. Clear stale
`forge_spans` on dirty rows to prevent `end_col` out-of-range errors
after edits like `dd`.

lua/pending/views.lua

@@ -1,6 +1,13 @@
 local config = require('pending.config')
+local forge = require('pending.forge')
 local parse = require('pending.parse')
 
+---@class pending.ForgeLineMeta
+---@field ref pending.ForgeRef
+---@field cache? pending.ForgeCache
+---@field col_start integer
+---@field col_end integer
+
 ---@class pending.LineMeta
 ---@field type 'task'|'header'|'blank'|'filter'
 ---@field id? integer
@@ -14,6 +21,7 @@ local parse = require('pending.parse')
 ---@field recur? string
 ---@field forge_ref? pending.ForgeRef
 ---@field forge_cache? pending.ForgeCache
+---@field forge_spans? pending.ForgeLineMeta[]
 
 ---@class pending.views
 local M = {}
@@ -43,6 +51,27 @@ local function format_due(due)
   return formatted
 end
 
+---@param task pending.Task
+---@param prefix_len integer
+---@return pending.ForgeLineMeta[]?
+local function compute_forge_spans(task, prefix_len)
+  local refs = forge.find_refs(task.description)
+  if #refs == 0 then
+    return nil
+  end
+  local cache = task._extra and task._extra._forge_cache or nil
+  local spans = {}
+  for _, r in ipairs(refs) do
+    table.insert(spans, {
+      ref = r.ref,
+      cache = cache,
+      col_start = prefix_len + r.start_byte,
+      col_end = prefix_len + r.end_byte,
+    })
+  end
+  return spans
+end
+
 ---@type table<string, integer>
 local status_rank = { wip = 0, pending = 1, blocked = 2, done = 3 }
 
@@ -178,6 +207,7 @@ function M.category_view(tasks)
       local prefix = '/' .. task.id .. '/'
       local state = state_char(task)
       local line = prefix .. '- [' .. state .. '] ' .. task.description
+      local prefix_len = #prefix + #('- [' .. state .. '] ')
       table.insert(lines, line)
       table.insert(meta, {
         type = 'task',
@@ -191,6 +221,7 @@ function M.category_view(tasks)
         recur = task.recur,
         forge_ref = task._extra and task._extra._forge_ref or nil,
         forge_cache = task._extra and task._extra._forge_cache or nil,
+        forge_spans = compute_forge_spans(task, prefix_len),
       })
     end
   end
@@ -231,6 +262,7 @@ function M.priority_view(tasks)
     local prefix = '/' .. task.id .. '/'
     local state = task.status == 'done' and 'x' or (task.priority > 0 and '!' or ' ')
     local line = prefix .. '- [' .. state .. '] ' .. task.description
+    local prefix_len = #prefix + #('- [' .. state .. '] ')
     table.insert(lines, line)
     table.insert(meta, {
       type = 'task',
@@ -245,6 +277,7 @@ function M.priority_view(tasks)
       recur = task.recur,
       forge_ref = task._extra and task._extra._forge_ref or nil,
       forge_cache = task._extra and task._extra._forge_cache or nil,
+      forge_spans = compute_forge_spans(task, prefix_len),
     })
   end