fix(diff): preserve due/rec when absent from buffer line (#68)

* fix(diff): preserve due/rec when absent from buffer line

Problem: `diff.apply` overwrites `task.due` and `task.recur` with `nil`
whenever those fields aren't present as inline tokens in the buffer line.
Because metadata is rendered as virtual text (never in the line text),
every description edit silently clears due dates and recurrence rules.

Solution: Only update `due`, `recur`, and `recur_mode` in the existing-
task branch when the parsed entry actually contains them (non-nil). Users
can still set/change these inline by typing `due:<date>` or `rec:<rule>`;
clearing them requires `:Pending edit <id> -due`.

* refactor: remove project-local store discovery

Problem: `store.resolve_path()` searched upward for `.pending.json`,
silently splitting task data across multiple files depending on CWD.

Solution: `resolve_path()` now always returns `config.get().data_path`.
Remove `M.init()` and the `:Pending init` command and tab-completion
entry. Remove the project-local health message.

* refactor: extract log.lua, standardise [pending.nvim]: prefix

Problem: Notifications were scattered across files using bare
`vim.notify` with inconsistent `pending.nvim: ` prefixes, and the
`debug` guard in `textobj.lua` and `init.lua` was duplicated inline.

Solution: Add `lua/pending/log.lua` with `info`, `warn`, `error`, and
`debug` functions (prefix `[pending.nvim]: `). `log.debug` only fires
when `config.debug = true` or the optional `override` param is `true`.
Replace all `vim.notify` callsites and remove inline debug guards.

* feat(parse): configurable input date formats

Problem: `due:` only accepted ISO `YYYY-MM-DD` and built-in keywords;
users expecting locale-style dates like `03/15/2026` or `15-Mar-2026`
had no way to configure alternative input formats.

Solution: Add `input_date_formats` config field (string[]). Each entry
is a strftime-like format string supporting `%Y`, `%y`, `%m`, `%d`,
`%e`, `%b`, `%B`. Formats are tried in order after built-in keywords
fail. When no year specifier is present the current or next year is
inferred. Update vimdoc and add 8 parse_spec tests.

lua/pending/sync/oauth.lua

@@ -1,4 +1,5 @@
 local config = require('pending.config')
+local log = require('pending.log')
 
 local TOKEN_URL = 'https://oauth2.googleapis.com/token'
 local AUTH_URL = 'https://accounts.google.com/o/oauth2/v2/auth'
@@ -247,7 +248,7 @@ function OAuthClient:get_access_token()
   if now - obtained > expires - 60 then
     tokens = self:refresh_access_token(creds, tokens)
     if not tokens then
-      vim.notify('pending.nvim: Failed to refresh access token.', vim.log.levels.ERROR)
+      log.error('Failed to refresh access token.')
       return nil
     end
   end
@@ -289,7 +290,7 @@ function OAuthClient:auth()
     .. '&code_challenge_method=S256'
 
   vim.ui.open(auth_url)
-  vim.notify('pending.nvim: Opening browser for Google authorization...')
+  log.info('Opening browser for Google authorization...')
 
   local server = vim.uv.new_tcp()
   local server_closed = false
@@ -337,7 +338,7 @@ function OAuthClient:auth()
   vim.defer_fn(function()
     if not server_closed then
       close_server()
-      vim.notify('pending.nvim: OAuth callback timed out (120s).', vim.log.levels.WARN)
+      log.warn('OAuth callback timed out (120s).')
     end
   end, 120000)
 end
@@ -373,19 +374,19 @@ function OAuthClient:_exchange_code(creds, code, code_verifier, port)
   }, { text = true })
 
   if result.code ~= 0 then
-    vim.notify('pending.nvim: Token exchange failed.', vim.log.levels.ERROR)
+    log.error('Token exchange failed.')
     return
   end
 
   local ok, decoded = pcall(vim.json.decode, result.stdout or '')
   if not ok or not decoded.access_token then
-    vim.notify('pending.nvim: Invalid token response.', vim.log.levels.ERROR)
+    log.error('Invalid token response.')
     return
   end
 
   decoded.obtained_at = os.time()
   self:save_tokens(decoded)
-  vim.notify('pending.nvim: ' .. self.name .. ' authorized successfully.')
+  log.info(self.name .. ' authorized successfully.')
 end
 
 ---@param opts { name: string, scope: string, port: integer, config_key: string }