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/parse.lua

@@ -10,7 +10,10 @@ local function is_valid_date(s)
   if not y then
     return false
   end
-  y, m, d = tonumber(y), tonumber(m), tonumber(d)
+  y, m, d =
+    tonumber(y), --[[@as integer]]
+    tonumber(m), --[[@as integer]]
+    tonumber(d) --[[@as integer]]
   if m < 1 or m > 12 then
     return false
   end
@@ -27,6 +30,60 @@ local function date_key()
   return config.get().date_syntax or 'due'
 end
 
+local weekday_map = {
+  sun = 1,
+  mon = 2,
+  tue = 3,
+  wed = 4,
+  thu = 5,
+  fri = 6,
+  sat = 7,
+}
+
+---@param text string
+---@return string|nil
+function M.resolve_date(text)
+  local lower = text:lower()
+  local today = os.date('*t')
+
+  if lower == 'today' then
+    return os.date('%Y-%m-%d', os.time({ year = today.year, month = today.month, day = today.day })) --[[@as string]]
+  end
+
+  if lower == 'tomorrow' then
+    return os.date(
+      '%Y-%m-%d',
+      os.time({ year = today.year, month = today.month, day = today.day + 1 })
+    ) --[[@as string]]
+  end
+
+  local n = lower:match('^%+(%d+)d$')
+  if n then
+    return os.date(
+      '%Y-%m-%d',
+      os.time({
+        year = today.year,
+        month = today.month,
+        day = today.day + (
+            tonumber(n) --[[@as integer]]
+          ),
+      })
+    ) --[[@as string]]
+  end
+
+  local target_wday = weekday_map[lower]
+  if target_wday then
+    local current_wday = today.wday
+    local delta = (target_wday - current_wday) % 7
+    return os.date(
+      '%Y-%m-%d',
+      os.time({ year = today.year, month = today.month, day = today.day + delta })
+    ) --[[@as string]]
+  end
+
+  return nil
+end
+
 ---@param text string
 ---@return string description
 ---@return { due?: string, cat?: string } metadata
@@ -39,11 +96,12 @@ function M.body(text)
   local metadata = {}
   local i = #tokens
   local dk = date_key()
-  local date_pattern = '^' .. vim.pesc(dk) .. ':(%d%d%d%d%-%d%d%-%d%d)$'
+  local date_pattern_strict = '^' .. vim.pesc(dk) .. ':(%d%d%d%d%-%d%d%-%d%d)$'
+  local date_pattern_any = '^' .. vim.pesc(dk) .. ':(.+)$'
 
   while i >= 1 do
     local token = tokens[i]
-    local due_val = token:match(date_pattern)
+    local due_val = token:match(date_pattern_strict)
     if due_val then
       if metadata.due then
         break
@@ -54,15 +112,28 @@ function M.body(text)
       metadata.due = due_val
       i = i - 1
     else
-      local cat_val = token:match('^cat:(%S+)$')
-      if cat_val then
-        if metadata.cat then
+      local raw_val = token:match(date_pattern_any)
+      if raw_val then
+        if metadata.due then
           break
         end
-        metadata.cat = cat_val
+        local resolved = M.resolve_date(raw_val)
+        if not resolved then
+          break
+        end
+        metadata.due = resolved
         i = i - 1
       else
-        break
+        local cat_val = token:match('^cat:(%S+)$')
+        if cat_val then
+          if metadata.cat then
+            break
+          end
+          metadata.cat = cat_val
+          i = i - 1
+        else
+          break
+        end
       end
     end
   end