feat(web): allow manual disconnect of offline remote threads

[rynfar]

Offline remote threads can remain visible after reconnect has failed. After 20 seconds of an unavailable connection, the thread banner now offers Disconnect server for user-managed remote environments. It disables the saved connection through the existing catalog command and returns home only if the same route is still open. Primary and desktop-managed local environments are excluded; drafts and outbox data are untouched. A click rechecks the current catalog and connection, so a stale button cannot disable an environment that has already reconnected or been removed.

Adapted from upstream 2d737465027b18cafd0c4704e9025b124bc94b2c. The existing Reconnect and Connections actions remain available. No automatic disconnect or server stop was added.

Validation: 6 focused timer/navigation tests; web typecheck and scoped lint passed (existing ChatView warnings); independent review passed staged SHA c86741692fdefc128825d46f7d4c1dbd6bb1da885be125c6328a4e4a4bd75a23. No browser runtime verification was authorized.

Model: GPT-6 Sol (low) via Codex harness, with root agent oversight.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	14.0 KiB	13.9 KiB	−42 B (−0.3%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.2 KiB	7.2 KiB	+1 B (+0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.8 KiB	6.7 KiB	−43 B (−0.6%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.0 KiB	58.0 KiB	−44 B (−0.1%)	66.4 KiB	✅
Codex	Live turn messages	10	9	−1 (−10.0%)	21	✅
Claude	Total thread wire	14.0 KiB	14.0 KiB	−10 B (−0.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.2 KiB	7.2 KiB	−16 B (−0.2%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.7 KiB	6.8 KiB	+6 B (+0.1%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.9 KiB	58.9 KiB	−44 B (−0.1%)	66.4 KiB	✅
Claude	Live turn messages	10	9	−1 (−10.0%)	21	✅

Baseline: 7ed3f71 · PR result: 31cf06c · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 115.6 KiB
• Claude decoded thread snapshot: 116.3 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.