fix(app): unread sessions show a bold title when stopped, not an overloaded status dot

[chphch]

The session-list status dot is overloaded: a session with unread results is forced to a solid blue dot — the same color as the "thinking" (running) state, differing only by a pulse — so a finished, idle session looks like it is still running until you open it (which clears the unread flag).

This decouples the two signals. The status dot always reflects true liveness (disconnected / thinking / waiting / permission), and unread is shown instead as a bold title — but only once the agent has stopped, never while it is still running, so a re-activated session never reads as unread mid-turn. Blue goes back to meaning exactly one thing: running. Applies to both the session list rows and the compact active-sessions group.

Gated behind an experimental expUnreadBoldTitle setting, off by default. With it off the upstream presentation is preserved exactly (blue status dot + "unread" text, default title weight). Users opt in from Settings → Features.

The bold is applied via the SemiBold font family (read titles are Regular) rather than a numeric fontWeight, because the web build sets font-synthesis: none and bundles no Bold(700) IBM Plex Sans face — a fontWeight: 700 override would render identically to the regular title on web.

Proof

Captured locally on web — standalone happy-server (PGlite) + Expo web, driven headlessly with Playwright. The row's computed font-family flips Regular → SemiBold at the exact moment the turn stops and the session becomes unread; it stays Regular the whole time the agent is running.

agent running → title not bold	turn stopped + unread → title bold, no marker dot

Note the leading status dot stays a true-liveness indicator across the transition (blue "thinking" while running → neutral once idle), and the old trailing blue accent dot is gone — unread is conveyed entirely by the title weight.

Verification

pnpm typecheck clean; app suite green.

[chphch]

Rebased onto current main (3cf9ce70f) — no conflicts; the home rework (c63c80ff3 / 6dc878dc3) rebuilt which container renders which sessions but never entered CompactSessionRow's status logic or SessionItem's title weight, so the problem and the fix are both unchanged.

One import fix was needed for tsc to pass: upstream has since added useSettingMutable to the storage import at SessionsList.tsx:5, which duplicated the one this PR added. Merged useSetting into upstream's line and dropped the added one.

pnpm typecheck clean; app suite 919/919.