fix(desktop): cross-machine session-list sync (pins/titles) — focus refresh + 30s focused poll

[Kyzcreig]

Ace repro'd both directions live: pin on Studio ≠ visible on MBP; unpin on MBP ≠ visible on Studio (until app restart).

Root cause: two mechanisms both stop at the machine boundary — session-sync.ts uses BroadcastChannel (same-machine renderer windows only), and gateway session.info events route to the session's OWNING transport only (write_json precedence: per-session transport first). A second desktop connected to the same gateway never hears about the mutation.

Fix: refresh the session list on window focus + a 30s poll while focused (mirrors the shipped livesync poll pattern). Reuses refreshSessions(); no new RPCs; pop-out windows excluded as before. Typecheck clean.

[greptile-apps]

Greptile Summary

This PR fixes cross-machine session-list sync (pins, titles, new sessions) by adding a window focus listener and a 30-second focused poll that calls refreshSessions() — mirroring the cron and messaging poll patterns already in place. Secondary/pop-out windows are correctly excluded via isSecondaryWindow().

• Adds a single useEffect to DesktopController that attaches a window focus listener and a setInterval(30s) guarded by document.hasFocus(), both calling refreshSessions() on each tick.
• Reuses the existing refreshSessions function with silent error handling (catch(() => undefined)), so no new RPC surface is introduced.

Confidence Score: 5/5

Safe to merge; the fix is narrowly scoped and all error paths are swallowed gracefully.

The change is a small, focused addition that reuses a well-exercised code path. The only notable divergence from the established polling pattern — missing the gatewayState guard — causes silent no-op failures rather than visible user impact.

apps/desktop/src/app/desktop-controller.tsx — the new effect is the only changed code; worth a second look for the missing gateway-state guard noted in the inline comment.

Important Files Changed

Filename	Overview
apps/desktop/src/app/desktop-controller.tsx	Adds a focus-triggered + 30s poll useEffect for cross-machine session-list sync; consistent with existing poll patterns but missing the gatewayState guard used by cron and messaging polls

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant W as Window (Machine B)
    participant DC as DesktopController
    participant RS as refreshSessions()
    participant GW as Gateway API

    Note over W,GW: Machine A pins/renames a session
    Note over W,DC: BroadcastChannel & session.info events never leave Machine A

    W->>DC: window 'focus' event
    DC->>RS: refresh()
    RS->>GW: fetch session list
    GW-->>RS: updated sessions (with Machine A's changes)
    RS-->>DC: sessions store updated

    Note over DC: 30s interval (while focused)
    loop Every 30s while document.hasFocus()
        DC->>RS: refresh()
        RS->>GW: fetch session list
        GW-->>RS: updated sessions
        RS-->>DC: sessions store updated
    end

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sequenceDiagram
    participant W as Window (Machine B)
    participant DC as DesktopController
    participant RS as refreshSessions()
    participant GW as Gateway API

    Note over W,GW: Machine A pins/renames a session
    Note over W,DC: BroadcastChannel & session.info events never leave Machine A

    W->>DC: window 'focus' event
    DC->>RS: refresh()
    RS->>GW: fetch session list
    GW-->>RS: updated sessions (with Machine A's changes)
    RS-->>DC: sessions store updated

    Note over DC: 30s interval (while focused)
    loop Every 30s while document.hasFocus()
        DC->>RS: refresh()
        RS->>GW: fetch session list
        GW-->>RS: updated sessions
        RS-->>DC: sessions store updated
    end

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