Reliably restore last session on refresh after a server restart

The page-load restore was one-shot and bailed when a completed scan's
replayed scan_phase left a running flag set; sse_replay_done (the other
retry) only fires for a non-empty replay buffer, which is empty after a
restart — so refreshing post-update showed a blank grid despite the
results being in the DB. The watchdog now retries the restore on each
4s poll while nothing is shown and no scan runs, clearing stale flags
first. /api/scan/status also reports google_running separately so a
refresh during a live Google scan is no longer treated as idle.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

static/js/CLAUDE.md

@@ -41,7 +41,7 @@ Never revert to `!!window._googleConnected` / `_fileSources.length > 0` — thos
 ## Scan history browser — history.js + results.js
 
 - **`S._historyRefScanId`** — `null` = live/SSE mode; positive int = viewing a past session. Set by `loadHistorySession()`; cleared by `exitHistoryMode()`.
-- **Auto-load on page load** — `results.js` calls `window.loadHistorySession?.(null)` once when the SSE watchdog confirms `!status.running`. `_initialStatusChecked` guard ensures this fires at most once per page load. The `sse_replay_done` handler in `scan.js` retries if `loadHistorySession` bailed due to stale running flags set during replay.
+- **Auto-load on page load** — `_sseWatchdog()` in `results.js` calls `window.loadHistorySession?.(null)` whenever `/api/scan/status` reports neither `running` (M365 + file lock) nor `google_running` (Google lock) **and** nothing is shown yet (`!S._historyRefScanId && !S.flaggedData.length`). This is **not one-shot** — it retries on every 4s poll until a session is restored, because (a) the replay buffer is empty after a server restart so `sse_replay_done` never fires, and (b) a completed scan's replayed `scan_phase` can leave a running flag set that would otherwise block the load forever. Because both locks are confirmed free, the watchdog clears the stale `_m365/_google/_fileScanRunning` flags before calling. Do not revert to a one-shot `_initialStatusChecked` gate — that reintroduces the "blank grid after refresh/restart" bug. `/api/scan/status` **must** report `google_running` separately; `running` alone misses live Google scans. The `sse_replay_done` handler in `scan.js` still retries for the non-empty-buffer (no-restart) case.
 - **History banner** (`#historyBanner`) — shown when `S._historyRefScanId` is set. Do not hide/show from outside `history.js`.
 - **Session picker** (`#historyDropdown`) — rendered inside `[data-history-wrap]` so the outside-click handler works correctly. Do not move the picker outside this wrapper.
 - **Cache invalidation** — `invalidateHistoryCache()` clears `_sessions` and `_latestRefScanId`. All three `*_done` SSE handlers call `window.invalidateHistoryCache?.()`.