feat: time-aware due dates, persistent undo, @return audit (#33)

* fix(plugin): allow command chaining with bar separator

Problem: :Pending|only failed because the command definition lacked the
bar attribute, causing | to be consumed as an argument.

Solution: Add bar = true to nvim_create_user_command so | is treated as
a command separator, matching fugitive's :Git behavior.

* refactor(buffer): remove opinionated window options

Problem: The plugin hardcoded number, relativenumber, wrap, spell,
signcolumn, foldcolumn, and cursorline in set_win_options, overriding
user preferences with no way to opt out.

Solution: Remove all cosmetic window options. Users who want them can
set them in after/ftplugin/pending.lua. Only conceallevel,
concealcursor, and winfixheight remain as functionally required.

* feat: time-aware due dates, persistent undo, @return audit

Problem: Due dates had no time component, the undo stack was lost on
restart and stored in a separate file, and many public functions lacked
required @return annotations.

Solution: Add YYYY-MM-DDThh:mm support across parse, views, recur,
complete, and init with time-aware overdue checks. Merge the undo stack
into the task store JSON so a single file holds all state. Add @return
nil annotations to all 27 void public functions across every module.

* feat(parse): flexible time parsing for @ suffix

Problem: the @HH:MM time suffix required zero-padded 24-hour format,
forcing users to write due:tomorrow@14:00 instead of due:tomorrow@2pm.

Solution: add normalize_time() that accepts bare hours (9, 14),
H:MM (9:30), am/pm (2pm, 9:30am, 12am), and existing HH:MM format,
normalizing all to canonical HH:MM on save.

* feat(complete): add info descriptions to omnifunc items

Problem: completion menu items had no description, making it hard to
distinguish between similar entries like date shorthands and recurrence
patterns.

Solution: return { word, info } tables from date_completions() and
recur_completions(), surfacing human-readable descriptions in the
completion popup.

* ci: format

lua/pending/complete.lua

@@ -29,48 +29,75 @@ local function get_categories()
   return result
 end
 
----@return string[]
+---@return { word: string, info: string }[]
 local function date_completions()
   return {
-    'today',
-    'tomorrow',
-    'yesterday',
-    '+1d',
-    '+2d',
-    '+3d',
-    '+1w',
-    '+2w',
-    '+1m',
-    'mon',
-    'tue',
-    'wed',
-    'thu',
-    'fri',
-    'sat',
-    'sun',
-    'eod',
-    'eow',
-    'eom',
-    'eoq',
-    'eoy',
-    'sow',
-    'som',
-    'soq',
-    'soy',
-    'later',
+    { word = 'today', info = "Today's date" },
+    { word = 'tomorrow', info = "Tomorrow's date" },
+    { word = 'yesterday', info = "Yesterday's date" },
+    { word = '+1d', info = '1 day from today' },
+    { word = '+2d', info = '2 days from today' },
+    { word = '+3d', info = '3 days from today' },
+    { word = '+1w', info = '1 week from today' },
+    { word = '+2w', info = '2 weeks from today' },
+    { word = '+1m', info = '1 month from today' },
+    { word = 'mon', info = 'Next Monday' },
+    { word = 'tue', info = 'Next Tuesday' },
+    { word = 'wed', info = 'Next Wednesday' },
+    { word = 'thu', info = 'Next Thursday' },
+    { word = 'fri', info = 'Next Friday' },
+    { word = 'sat', info = 'Next Saturday' },
+    { word = 'sun', info = 'Next Sunday' },
+    { word = 'eod', info = 'End of day (today)' },
+    { word = 'eow', info = 'End of week (Sunday)' },
+    { word = 'eom', info = 'End of month' },
+    { word = 'eoq', info = 'End of quarter' },
+    { word = 'eoy', info = 'End of year (Dec 31)' },
+    { word = 'sow', info = 'Start of week (Monday)' },
+    { word = 'som', info = 'Start of month' },
+    { word = 'soq', info = 'Start of quarter' },
+    { word = 'soy', info = 'Start of year (Jan 1)' },
+    { word = 'later', info = 'Someday (sentinel date)' },
+    { word = 'today@08:00', info = 'Today at 08:00' },
+    { word = 'today@09:00', info = 'Today at 09:00' },
+    { word = 'today@10:00', info = 'Today at 10:00' },
+    { word = 'today@12:00', info = 'Today at 12:00' },
+    { word = 'today@14:00', info = 'Today at 14:00' },
+    { word = 'today@17:00', info = 'Today at 17:00' },
   }
 end
 
----@return string[]
+---@type table<string, string>
+local recur_descriptions = {
+  daily = 'Every day',
+  weekdays = 'Monday through Friday',
+  weekly = 'Every week',
+  biweekly = 'Every 2 weeks',
+  monthly = 'Every month',
+  quarterly = 'Every 3 months',
+  yearly = 'Every year',
+  ['2d'] = 'Every 2 days',
+  ['3d'] = 'Every 3 days',
+  ['2w'] = 'Every 2 weeks',
+  ['3w'] = 'Every 3 weeks',
+  ['2m'] = 'Every 2 months',
+  ['3m'] = 'Every 3 months',
+  ['6m'] = 'Every 6 months',
+  ['2y'] = 'Every 2 years',
+}
+
+---@return { word: string, info: string }[]
 local function recur_completions()
   local recur = require('pending.recur')
   local list = recur.shorthand_list()
   local result = {}
   for _, s in ipairs(list) do
-    table.insert(result, s)
+    local desc = recur_descriptions[s] or s
+    table.insert(result, { word = s, info = desc })
   end
   for _, s in ipairs(list) do
-    table.insert(result, '!' .. s)
+    local desc = recur_descriptions[s] or s
+    table.insert(result, { word = '!' .. s, info = desc .. ' (from completion date)' })
   end
   return result
 end
@@ -111,24 +138,29 @@ function M.omnifunc(findstart, base)
     return -1
   end
 
-  local candidates = {}
+  local matches = {}
   local source = _complete_source or ''
 
   local dk = date_key()
   local rk = recur_key()
 
   if source == dk then
-    candidates = date_completions()
+    for _, c in ipairs(date_completions()) do
+      if base == '' or c.word:sub(1, #base) == base then
+        table.insert(matches, { word = c.word, menu = '[' .. source .. ']', info = c.info })
+      end
+    end
   elseif source == 'cat' then
-    candidates = get_categories()
+    for _, c in ipairs(get_categories()) do
+      if base == '' or c:sub(1, #base) == base then
+        table.insert(matches, { word = c, menu = '[cat]' })
+      end
+    end
   elseif source == rk then
-    candidates = recur_completions()
-  end
-
-  local matches = {}
-  for _, c in ipairs(candidates) do
-    if base == '' or c:sub(1, #base) == base then
-      table.insert(matches, { word = c, menu = '[' .. source .. ']' })
+    for _, c in ipairs(recur_completions()) do
+      if base == '' or c.word:sub(1, #base) == base then
+        table.insert(matches, { word = c.word, menu = '[' .. source .. ']', info = c.info })
+      end
     end
   end