feat(textobj): add debug mode, rename priority view buffer

Problem: the ]] motion reportedly lands one line past the header in
some environments, and ]t/[t may not override Neovim defaults. No
way to diagnose these at runtime. Also, pending://priority is a poor
buffer name for the flat ranked view.

Solution: add a debug config option (vim.g.pending = { debug = true })
that logs meta state, cursor positions, and mapping registration to
:messages at DEBUG level. Rename the buffer from pending://priority to
pending://queue. Internal view identifier stays 'priority'.

lua/pending/config.lua

@@ -30,6 +30,7 @@
 ---@field someday_date string
 ---@field category_order? string[]
 ---@field drawer_height? integer
+---@field debug? boolean
 ---@field keymaps pending.Keymaps
 ---@field gcal? pending.GcalConfig