fix(buffer): correct extmark drift on open_line for done tasks (#118)

* fix(config): update default keymaps to match vimdoc

Problem: four keymap defaults in `config.lua` still used the old
deprecated keys (`!`, `D`, `U`, `F`) while `doc/pending.txt` documents
the `g`-prefixed replacements (`g!`, `gd`, `gz`, `gf`).

Solution: update `priority`, `date`, `undo`, and `filter` defaults to
`g!`, `gd`, `gz`, and `gf` respectively.

* fix(buffer): correct extmark drift on `open_line` above/below done tasks

Problem: `open_line` used `nvim_buf_set_lines` which triggered `on_bytes`
with a `start_row` offset designed for native `o`/`O` keypresses. The
`_meta` entry was inserted one position too late, causing the done task's
`PendingDone` highlight to attach to the new blank line instead.

Solution: suppress `on_bytes` during `open_line` by reusing the
`_rendering` guard, insert the meta entry at the correct position, and
immediately reapply inline extmarks for the affected rows.

* fix(buffer): infer task status from line text in `reapply_dirty_inline`

Problem: `on_bytes` inserts bare `{ type = 'task' }` meta entries with
no `status` field for any new lines (paste, undo, native edits). When
meta positions also shift incorrectly (e.g. `P` paste above), existing
meta with the wrong status ends up on the wrong row. This causes done
tasks to lose their `PendingDone` highlight and pending tasks to appear
greyed out.

Solution: always re-infer `status` from the actual buffer line text for
dirty task rows before applying extmarks. The checkbox character (`[x]`,
`[>]`, `[=]`, `[ ]`) is the source of truth, with fallback to the
existing meta status if the line doesn't match a task pattern.

lua/pending/buffer.lua

@@ -182,6 +182,23 @@ local function apply_inline_row(bufnr, row, m, icons)
   end
 end
 
+---@param line string
+---@return string?
+local function infer_status(line)
+  local ch = line:match('^/%d+/- %[(.)%]') or line:match('^- %[(.)%]')
+  if not ch then
+    return nil
+  end
+  if ch == 'x' then
+    return 'done'
+  elseif ch == '>' then
+    return 'wip'
+  elseif ch == '=' then
+    return 'blocked'
+  end
+  return 'pending'
+end
+
 ---@param bufnr integer
 ---@return nil
 function M.reapply_dirty_inline(bufnr)
@@ -191,6 +208,10 @@ function M.reapply_dirty_inline(bufnr)
   local icons = config.get().icons
   for row in pairs(_dirty_rows) do
     local m = _meta[row]
+    if m and m.type == 'task' then
+      local line = vim.api.nvim_buf_get_lines(bufnr, row - 1, row, false)[1] or ''
+      m.status = infer_status(line) or m.status
+    end
     if m then
       vim.api.nvim_buf_clear_namespace(bufnr, ns_inline, row - 1, row)
       apply_inline_row(bufnr, row - 1, m, icons)
@@ -345,8 +366,25 @@ function M.open_line(above)
   end
   local row = vim.api.nvim_win_get_cursor(0)[1]
   local insert_row = above and (row - 1) or row
+  local meta_pos = insert_row + 1
+
+  _rendering = true
   vim.bo[bufnr].modifiable = true
   vim.api.nvim_buf_set_lines(bufnr, insert_row, insert_row, false, { '- [ ] ' })
+  _rendering = false
+
+  table.insert(_meta, meta_pos, { type = 'task' })
+
+  local icons = config.get().icons
+  local total = vim.api.nvim_buf_line_count(bufnr)
+  for r = meta_pos, math.min(meta_pos + 1, total) do
+    vim.api.nvim_buf_clear_namespace(bufnr, ns_inline, r - 1, r)
+    local m = _meta[r]
+    if m then
+      apply_inline_row(bufnr, r - 1, m, icons)
+    end
+  end
+
   vim.api.nvim_win_set_cursor(0, { insert_row + 1, 6 })
   vim.cmd('startinsert!')
 end