Add a shell-level auto-refresh pause/resume control (#4222)

[erikdarlingdata]

Refs #4222.

Why

Erik's ruling on #4222 (alert-notebook MVP): the notebook must be LIVE, not frozen, and the operator needs a shell-level play/pause control for the 60s auto-refresh — usable on every page, not just the alert-notebook view. Before this change, the refresh loop in app.js only paused automatically while the browser tab was hidden; there was no way for an operator to stop it on a visible tab (for example, while reading a notebook mid-incident) short of closing the tab.

What changes

• Shell chrome: a real <button id="auto-refresh-toggle"> added to the sidebar's brand block in index.html, so it renders once and survives every route change (it lives outside #main, which every page render replaces).
• app.js:
  • initAutoRefreshToggle() wires the button, sets its label/aria-label/title to "Pause auto-refresh" / "Resume auto-refresh", and toggles aria-pressed.
  • State persists under the darling.autoRefreshPaused localStorage key (isAutoRefreshPaused/setAutoRefreshPaused), so it survives a reload or navigation.
  • Both poll paths — the 60s setInterval tick and the visibilitychange handler — check !isAutoRefreshPaused() in addition to the existing !document.hidden check. The existing hidden-tab pause is unchanged; the new control is an independent gate on top of it.
  • Resuming (clicking the button while paused) runs one refresh() immediately, rather than waiting out whatever is left of the 60s window.
  • refresh()'s existing poll-skip guard (editor/notebookEditor/alertEditor routes) now also skips #/triage — the alert-notebook deep-link landing page. The fix-shape draft's cost item said the periodic tick must not re-render triage every 60s; this reuses the exact same guard line the composer routes already use, computed before the sidebar/view-list/AG-nav reads start their own tick. Nothing else about the triage page changed.
• app.css: a small pill-style button (.auto-refresh-toggle) using the existing theme variables (--muted, --accent, --border, --fg); no new colors introduced.
• Test: Darling.Tests/WebFetchLayerTests.cs gets three new source pins (this repo has no JS test runner, so these are text-scan pins over the shipped module, same pattern as the existing AppJs_RefreshSkips... tests):
  • AppJs_RefreshSkipsTriageRouteToo — pins that routeName === "triage" is in the guard and runs before this tick's own reads start.
  • AppJs_HasAShellLevelAutoRefreshPauseThatGatesBothPollPaths — pins the localStorage key, the toggle functions, and that BOTH poll paths (interval + visibilitychange) check the paused flag, not just document.hidden.
  • IndexHtml_HasTheAutoRefreshToggleButtonInTheShellChrome — pins the button markup lives in the shell chrome.

Not in this slice: the /api/alert-notebook endpoint, the notebook read cell type, and views.js are other #4222 lanes' files and were not touched. #4191 (aborting superseded reads) is not implemented here; the new pause/resume gate is orthogonal to that later re-entrancy guard and does not block it.

Test plan

• dotnet build Darling/Darling.Tests/Darling.Tests.csproj -p:EnableWindowsTargeting=true — 0 warnings, 0 errors (macOS, cross-compiled; Darling.Tests targets net10.0-windows and cannot run here — CI decides the full class).
• dotnet build Lite.Tests/Lite.Tests.csproj -p:EnableWindowsTargeting=true — 0 warnings, 0 errors (untouched by this change; built to confirm nothing else broke).
• WebFetchLayerTests (new pins) — CI decides.
• Full Windows test suite — CI decides.

Lite parity: N/A. This is Darling web viewer only; Lite is the WPF desktop app and has no browser tab or localStorage.

CHANGELOG entry

SECTION: Added
ENTRY:

• A shell-level pause/resume control for the web viewer's auto-refresh ([Add a shell-level auto-refresh pause/resume control (#4222) #4365]) - the 60s refresh loop previously only paused automatically while a browser tab was hidden. Added a button in the sidebar chrome, present on every page, that lets the operator pause and resume the tick directly; the paused state persists across reloads. Resuming runs one refresh immediately. Also added the alert-notebook triage deep-link route to the existing poll-skip guard so the periodic tick does not re-render it.
  REF:
  [Add a shell-level auto-refresh pause/resume control (#4222) #4365]: Add a shell-level auto-refresh pause/resume control (#4222) #4365

For the coordinator

• New shell control: #auto-refresh-toggle button in index.html's sidebar brand block. Other Alert notebook MVP: #/triage renders a read-only notebook bound to the firing (blocking and deadlocks authored, every other family converted) #4222 slices (the /api/alert-notebook endpoint, the read cell type) do not need to reference it directly — the pause state is read only by app.js's own refresh()/interval/visibilitychange paths.
• refresh()'s route-skip guard in app.js now includes routeName === "triage". If a later slice adds its own poll-sensitive route, extend that same guard line rather than adding a second guard.
• localStorage key used: darling.autoRefreshPaused (string "1" when paused, absent otherwise). No other slice should reuse this key.
• Left for later (explicitly out of scope for this slice, per the brief): Web viewer: the 60 s poll and tab switches re-fire a page's reads while the previous render's reads are still running, and superseded reads are never cancelled #4191's re-entrancy/abort guard in refresh(). The pause/resume gate here is additive and does not need changes when that lands.