fix(settings): report rejected shared-settings writes on every environment

[juliusmarminge]

Problem

#9147 made auto-settle, thread env mode and source control writing style fan out to every connected environment, with a "Settings differ / Apply to all" row when one holds a different value. A rejected write (dropped session, server that refuses orchestration:operate, a settings file that cannot be written) only reached console.warn. On mobile that meant "Apply to all" and the auto-settle switches looked saved while nothing changed and the mismatch row never cleared. Web had the same gap.

Mobile also decided "connected" with a looser check than web, so it listed environments as mismatched that it could never write to.

Fix

• Await each fan-out write and name every environment that rejected it, each with its own reason: Alert on mobile, error toast on web. Accepted writes already come back through the config subscription, so no optimistic state is added.
• Move supportsSharedSettings (connected + threadAutoSettlement capability) into packages/client-runtime/state/shared-settings so web and mobile agree on which environments are write targets. Tests added.
• Mobile: drop the duplicated day count from the inactive-threads row (the field below already shows it), per Wout's note.

Proof

Two dev servers on this box, both connected from one web client. Environment B (nucbox-1 in the remote list) has its userdata directory made read-only so its settings.json write fails with a real ServerSettingsError; environment A accepts the same write.

Before — same rejected write on main. The mismatch banner appears because B still holds the old value, but nothing tells the user the write failed or why:

After — the write is reported with the environment name and the server's reason:

Apply to all on the mismatch banner fails the same way and says so; once B can write again the same button succeeds and the banner clears:

Full run (toggle with both healthy → B goes read-only → toggle → Apply to all rejected → B restored → Apply to all clears):

https://gh-file-drop-api-prod-mi5fy3sowv63ufte.pinglabs.workers.dev/f/178486f7368218cf/after-demo.webm

Mobile shares the same writeTo/describeRejectedSettingsWrites path with an Alert instead of a toast; no simulator on this machine to record it.

Surfaces

• Web (Settings → General, Source Control), mobile (Settings → General). Desktop wraps web.
• docs/user/thread-sidebar.md updated.

Written by Claude Fable 5 in Claude Code.

🤖 Generated with Claude Code

[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	13.8 KiB	13.8 KiB	0 B (0.0%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.0 KiB	7.0 KiB	−1 B (−0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.7 KiB	6.7 KiB	+1 B (+0.0%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.5 KiB	58.5 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	10	10	0 (0.0%)	21	✅
Claude	Total thread wire	13.6 KiB	13.6 KiB	−14 B (−0.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.0 KiB	7.0 KiB	−1 B (−0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.6 KiB	6.6 KiB	−13 B (−0.2%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.9 KiB	57.9 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	10	10	0 (0.0%)	21	✅

Baseline: 854541a · PR result: 357af8f · 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: 113.8 KiB
• Claude decoded thread snapshot: 114.5 KiB

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

[macroscopeapp]

Approvability

Verdict: Approved at 357af8f

Macroscope's review found this PR approvable — This is a contained settings bug fix that reports rejected fan-out writes per environment while preserving successful writes and subscription-driven updates. The remaining changes are shared predicate/test coverage, mobile copy cleanup, and documentation, with no schema, deployment, security, billing, or default-setting impact.

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