feat: complete task editing coverage (#109)

Problem: the task editing surface had gaps — category and recurrence had
no keymaps, `:Pending edit` required knowing the task ID, tasks couldn't
be reordered with a keymap, priority was binary (0/1), and `wip`/`blocked`
states were documented but unimplemented.

Solution: fill every cell so every property is editable in every way.

- `gc`/`gr` keymaps for category select and recurrence prompt
- cursor-aware `:Pending edit` (omit ID to use task under cursor)
- `J`/`K` keymaps to reorder tasks within a category
- multi-level priorities (`max_priority` config, `g!` cycles 0→1→2→3→0)
- `+!!`/`+!!!` tokens in `:Pending edit`, `:Pending add`, `parse.body()`
- `PendingPriority2`/`PendingPriority3` highlight groups
- `gw`/`gb` keymaps toggle `wip`/`blocked` status
- `>`/`=` state chars in buffer rendering and diff parsing
- `PendingWip`/`PendingBlocked` highlight groups
- sort order: wip → pending → blocked → done
- `wip`/`blocked` filter predicates and icons

lua/pending/config.lua

@@ -9,6 +9,8 @@
 ---@field pending string
 ---@field done string
 ---@field priority string
+---@field wip string
+---@field blocked string
 ---@field due string
 ---@field recur string
 ---@field category string
@@ -48,6 +50,12 @@
 ---@field prev_header? string|false
 ---@field next_task? string|false
 ---@field prev_task? string|false
+---@field category? string|false
+---@field recur? string|false
+---@field move_down? string|false
+---@field move_up? string|false
+---@field wip? string|false
+---@field blocked? string|false
 
 ---@class pending.CategoryViewConfig
 ---@field order? string[]
@@ -73,6 +81,7 @@
 ---@field debug? boolean
 ---@field keymaps pending.Keymaps
 ---@field view pending.ViewConfig
+---@field max_priority? integer
 ---@field sync? pending.SyncConfig
 ---@field icons pending.Icons
 
@@ -87,6 +96,7 @@ local defaults = {
   date_syntax = 'due',
   recur_syntax = 'rec',
   someday_date = '9999-12-30',
+  max_priority = 3,
   view = {
     default = 'category',
     eol_format = '%c  %r  %d',
@@ -114,12 +124,20 @@ local defaults = {
     prev_header = '[[',
     next_task = ']t',
     prev_task = '[t',
+    category = 'gc',
+    recur = 'gr',
+    move_down = 'J',
+    move_up = 'K',
+    wip = 'gw',
+    blocked = 'gb',
   },
   sync = {},
   icons = {
     pending = ' ',
     done = 'x',
     priority = '!',
+    wip = '>',
+    blocked = '=',
     due = '.',
     recur = '~',
     category = '#',