feat: overdue highlighting, relative dates, undo write, buffer mappings (#1)

* feat(config): add category_order field

Problem: category display order was always insertion order with no way
to configure it.

Solution: add category_order to config defaults so users can declare a
preferred category ordering; unspecified categories append after.

* feat(parse): add relative date resolution

Problem: due dates required full YYYY-MM-DD input, adding friction for
common cases like "today" or "next monday".

Solution: add resolve_date() supporting today, tomorrow, +Nd, and
weekday abbreviations; extend inline token parsing to resolve relative
values before falling back to strict date validation.

* feat(views): overdue flag, category in priority view, category ordering

Problem: overdue tasks were visually indistinct from upcoming ones;
priority view had no category context; category display order was not
configurable.

Solution: compute overdue meta flag for pending tasks past their due
date; set show_category on priority view task meta; reorder categories
according to config.category_order when present.

* feat(buffer): overdue highlight, category virt text in priority view

Problem: overdue tasks had no visual distinction; priority view showed
no category context alongside due dates.

Solution: add PendingOverdue highlight group; render category name as
right-aligned virtual text in priority view, composited with the due
date when both are present.

* feat(init): undo write and buffer-local default mappings

Problem: _undo_state was captured on every save but never consumed;
toggle_priority and prompt_date had no buffer-local defaults, requiring
manual <Plug> configuration.

Solution: implement undo_write() to restore pre-save task state; add !,
d, and U as buffer-local defaults following fugitive's philosophy of
owning the buffer; expose :Pending undo as a command alias.

* test(views): add views spec

Problem: views.lua had no test coverage.

Solution: add 26 tests covering category_view and priority_view
including sort order, line format, overdue detection, show_category
meta, and category_order config behavior.

* test(archive): add archive spec

Problem: archive had no test coverage.

Solution: add 9 tests covering cutoff logic, custom day counts, pending
task preservation, deleted task cleanup, and notify output.

* docs: add vimdoc

Problem: no :help documentation existed.

Solution: add doc/pending.txt covering all features — commands,
mappings, views, configuration, Google Calendar sync, highlight groups,
data format, and health check — following standard vimdoc conventions.

* ci: format

* fix: resolve lint and type check errors

Problem: selene flagged unused variables in new spec files; LuaLS
flagged os.date/os.time return type mismatches, integer? assignments,
and stale task.Task/task.GcalConfig type references.

Solution: prefix unused spec variables with _ or drop unnecessary
assignments; add --[[@as string/integer]] casts for os.date and
os.time calls; add category_order field to pending.Config annotation;
fix task.GcalConfig -> pending.GcalConfig and task.Task[] ->
pending.Task[]; add nil guards on meta[row].id before store calls;
cast store.data() return to non-optional.

* ci: format

* fix: sync

* ci: format

lua/pending/init.lua

@@ -41,6 +41,15 @@ function M._setup_buf_mappings(bufnr)
   vim.keymap.set('n', 'g?', function()
     M.show_help()
   end, opts)
+  vim.keymap.set('n', '!', function()
+    M.toggle_priority()
+  end, opts)
+  vim.keymap.set('n', 'd', function()
+    M.prompt_date()
+  end, opts)
+  vim.keymap.set('n', 'U', function()
+    M.undo_write()
+  end, opts)
 end
 
 ---@param bufnr integer
@@ -51,6 +60,17 @@ function M._on_write(bufnr)
   buffer.render(bufnr)
 end
 
+function M.undo_write()
+  if not _undo_state then
+    vim.notify('Nothing to undo.', vim.log.levels.WARN)
+    return
+  end
+  store.replace_tasks(_undo_state)
+  store.save()
+  _undo_state = nil
+  buffer.render(buffer.bufnr())
+end
+
 function M.toggle_complete()
   local bufnr = buffer.bufnr()
   if not bufnr then
@@ -62,6 +82,9 @@ function M.toggle_complete()
     return
   end
   local id = meta[row].id
+  if not id then
+    return
+  end
   local task = store.get(id)
   if not task then
     return
@@ -86,6 +109,9 @@ function M.toggle_priority()
     return
   end
   local id = meta[row].id
+  if not id then
+    return
+  end
   local task = store.get(id)
   if not task then
     return
@@ -107,13 +133,19 @@ function M.prompt_date()
     return
   end
   local id = meta[row].id
+  if not id then
+    return
+  end
   vim.ui.input({ prompt = 'Due date (YYYY-MM-DD): ' }, function(input)
     if not input then
       return
     end
     local due = input ~= '' and input or nil
     if due then
-      if not due:match('^%d%d%d%d%-%d%d%-%d%d$') then
+      local resolved = parse.resolve_date(due)
+      if resolved then
+        due = resolved
+      elseif not due:match('^%d%d%d%d%-%d%d%-%d%d$') then
         vim.notify('Invalid date format. Use YYYY-MM-DD.', vim.log.levels.ERROR)
         return
       end
@@ -170,12 +202,12 @@ function M.archive(days)
       local y, mo, d, h, mi, s = task['end']:match('^(%d+)-(%d+)-(%d+)T(%d+):(%d+):(%d+)Z$')
       if y then
         local t = os.time({
-          year = tonumber(y),
-          month = tonumber(mo),
-          day = tonumber(d),
-          hour = tonumber(h),
-          min = tonumber(mi),
-          sec = tonumber(s),
+          year = tonumber(y) --[[@as integer]],
+          month = tonumber(mo) --[[@as integer]],
+          day = tonumber(d) --[[@as integer]],
+          hour = tonumber(h) --[[@as integer]],
+          min = tonumber(mi) --[[@as integer]],
+          sec = tonumber(s) --[[@as integer]],
         })
         if t < cutoff then
           archived = archived + 1
@@ -203,6 +235,9 @@ function M.show_help()
     '',
     '<CR>     Toggle complete/uncomplete',
     '<Tab>    Switch category/priority view',
+    '!        Toggle priority',
+    'd        Set due date',
+    'U        Undo last write',
     'o / O    Add new task line',
     'dd       Delete task (on :w)',
     'p / P    Paste (duplicates get new IDs)',
@@ -212,6 +247,7 @@ function M.show_help()
     ':Pending add Cat: <text>     Quick-add with category',
     ':Pending sync                Push to Google Calendar',
     ':Pending archive [days]      Purge old done tasks',
+    ':Pending undo               Undo last write',
     '',
     'Inline metadata (on new lines before :w):',
     '  ' .. dk .. ':YYYY-MM-DD    Set due date',
@@ -256,6 +292,8 @@ function M.command(args)
   elseif cmd == 'archive' then
     local d = rest ~= '' and tonumber(rest) or nil
     M.archive(d)
+  elseif cmd == 'undo' then
+    M.undo_write()
   else
     vim.notify('Unknown Pending subcommand: ' .. cmd, vim.log.levels.ERROR)
   end