refactor: formatting fixes, config cleanup, health simplification

Problem: Formatter disagreements in `init.lua` and `gtasks.lua`,
stale `calendar` field in gcal config, and redundant health checks
for data directory existence.

Solution: Apply stylua formatting, remove `calendar` field from
`pending.GcalConfig`, drop data-dir and no-file health messages,
add `done`/`pending` to filter tab-completion candidates.

lua/pending/init.lua

@@ -559,10 +559,7 @@ local function run_sync(backend_name, action)
       end
     end
     table.sort(actions)
-    vim.notify(
-      backend_name .. ' actions: ' .. table.concat(actions, ', '),
-      vim.log.levels.INFO
-    )
+    vim.notify(backend_name .. ' actions: ' .. table.concat(actions, ', '), vim.log.levels.INFO)
     return
   end
   if type(backend[action]) ~= 'function' then