fix(statusline): GET /api/settings never writes, and a save sends the collection switch only on a flip

Two follow-ups to #361's sticky telemetry switch.

GET /api/settings reconciled an absent showPlanUsageLimits by persisting
true, but readJsonConfig() answers {} for ANY read failure (a parse
error, EACCES, EMFILE, a read landing inside PUT's non-atomic write), not
only ENOENT, and every page load calls this route, so one unlucky read
replaced the whole settings file with a one-key file. The route is a
plain read again and the default moved into the reader:
readPlanUsageTelemetryEnabled() treats an absent key as ON, the same way
readWorkspaceHooksEnabled() does, which is what the desktop chip already
shows for an install that never touched the setting.

saveAppSettings() sent showPlanUsageLimits on every save. The chip
defaults OFF on handhelds, so a phone saving its font size persisted
false and switched collection off for every desktop, whose chip then
went stale with no error anywhere. The key is now stripped like the
other per-device display keys and re-added only when the save FLIPS the
chip relative to what the device had (planUsageCollectionFlip), so an
explicit toggle on any device still writes it in either direction.

Tests pin both: the GET route with a mocked filesystem (absent, missing,
EACCES, garbage, explicit), the reader default, and the flip helper plus
its wiring in saveAppSettings.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/architecture-invariants.md

@@ -92,7 +92,7 @@ Tests: `test/docker-hosts.test.ts`, `test/docker-exec-options.test.ts`, `test/do
 
 ### Plan-usage chip (statusLine telemetry)
 
-**Plan-usage chip** (`showPlanUsageLimits`, per-device: desktop default **ON** since 1.9.3, handhelds OFF) renders compact Claude and Codex provider rows. Claude Code (v2.1.80+) pipes a JSON blob to a configured `statusLine.command` on each render; on Pro/Max it carries a `rate_limits` object (`five_hour`/`seven_day` windows only — no Opus weekly field — each `{used_percentage 0-100, resets_at epoch-SECONDS}`). ⚠️ **Injected as an EPHEMERAL `claude --settings` CLI flag at spawn (2026-09-07), never written to disk** — `resolveStatusLineCliCommand()`/`ensureStatusLineExporterScript()` in `hooks-config.ts` (`generateStatusLineCommand()`/`applyStatusLineConfig()` remain, but only as the legacy disk-write self-heal path: a workspace an older Codeman build touched gets its stale `.claude/settings.local.json` entry stripped the first time a session starts there again). The exporter WRAPS a user's own real statusline (`findEffectiveUserStatusLineCommand()`, walking Claude Code's own settings precedence) rather than replacing it, and POSTs the `rate_limits` blob to `POST /api/status-telemetry`. That route (auth-exempt like `/api/hook-event` — localhost-only, hook-secret-gated whenever auth is active, COD-91) parses via `usage-telemetry.ts` (pure, unit-tested), broadcasts SSE `session:statusTelemetry` (de-duped per session by `telemetrySignature` since the statusline fires on every assistant message), and returns a compact plain-text footer for the exporter to **print-through** (foreground POST in the no-wrap branch so its own stdout becomes the footer, `|| echo codeman` on failure; backgrounded — `>/dev/null 2>&1 </dev/null &`, closing stdin too — only in the wrap branch, where the user's own command owns the footer; `curl --max-time 5` bounds a hung, not just refused, Codeman). Main Codex subscription usage comes from the signed-in host CLI's read-only app-server `account/rateLimits/read` request at startup and every 5 minutes; `usage-telemetry.ts` selects only the main `codex` bucket (never model-specific buckets such as Spark), maps whatever 5-hour/7-day windows it supplies, and omits the provider row when unavailable. Credentials stay inside the CLI and no auth material is sent to the browser. `plan-usage-latest.ts` merges both process-wide sources and replays them in the SSE init snapshot (`getLightState`) so `#planUsageChip` renders immediately on page load/reconnect. `planUsageChipEnabled()` remains the single resolver behind the checkbox and chip visibility (DISPLAY only) — the SAME `showPlanUsageLimits` setting also doubles as the server-side telemetry COLLECTION switch, read FRESH from `settings.json` by `readPlanUsageTelemetryEnabled()` at every claude session create/respawn (`TmuxManager.createSession`/`respawnPane`), never cached, with no per-session field and no per-request wire field — applies uniformly across every claude-creation path (interactive Run, cron, Ralph Loop API, quick-start) and survives a Codeman restart by construction (nothing per-session to lose). Registry-gated on `getCli(mode)?.capabilities.statusLineTelemetry` rather than a hardcoded mode string. **Distinct from auto-resume** (which reacts to the Claude limit _message_; this proactively shows live percentages). Design: `docs/usage-limits-display-plan.md`. Tests: `test/usage-telemetry.test.ts`, `test/codex-plan-usage.test.ts`, `test/plan-usage-chip.test.ts`, `test/plan-usage-latest.test.ts`, `test/hooks-config.test.ts` (statusline exporter script + `readPlanUsageTelemetryEnabled`), `test/statusline-cli-flag.test.ts`.
+**Plan-usage chip** (`showPlanUsageLimits`, per-device: desktop default **ON** since 1.9.3, handhelds OFF) renders compact Claude and Codex provider rows. Claude Code (v2.1.80+) pipes a JSON blob to a configured `statusLine.command` on each render; on Pro/Max it carries a `rate_limits` object (`five_hour`/`seven_day` windows only — no Opus weekly field — each `{used_percentage 0-100, resets_at epoch-SECONDS}`). ⚠️ **Injected as an EPHEMERAL `claude --settings` CLI flag at spawn (2026-09-07), never written to disk** — `resolveStatusLineCliCommand()`/`ensureStatusLineExporterScript()` in `hooks-config.ts` (`generateStatusLineCommand()`/`applyStatusLineConfig()` remain, but only as the legacy disk-write self-heal path: a workspace an older Codeman build touched gets its stale `.claude/settings.local.json` entry stripped the first time a session starts there again). The exporter WRAPS a user's own real statusline (`findEffectiveUserStatusLineCommand()`, walking Claude Code's own settings precedence) rather than replacing it, and POSTs the `rate_limits` blob to `POST /api/status-telemetry`. That route (auth-exempt like `/api/hook-event` — localhost-only, hook-secret-gated whenever auth is active, COD-91) parses via `usage-telemetry.ts` (pure, unit-tested), broadcasts SSE `session:statusTelemetry` (de-duped per session by `telemetrySignature` since the statusline fires on every assistant message), and returns a compact plain-text footer for the exporter to **print-through** (foreground POST in the no-wrap branch so its own stdout becomes the footer, printing NOTHING on failure, `curl -sfk` plus `|| true`, since a bare brand word on the statusline is what discussion #405 opened with; backgrounded — `>/dev/null 2>&1 </dev/null &`, closing stdin too — only in the wrap branch, where the user's own command owns the footer; `curl --max-time 5` bounds a hung, not just refused, Codeman). Main Codex subscription usage comes from the signed-in host CLI's read-only app-server `account/rateLimits/read` request at startup and every 5 minutes; `usage-telemetry.ts` selects only the main `codex` bucket (never model-specific buckets such as Spark), maps whatever 5-hour/7-day windows it supplies, and omits the provider row when unavailable. Credentials stay inside the CLI and no auth material is sent to the browser. `plan-usage-latest.ts` merges both process-wide sources and replays them in the SSE init snapshot (`getLightState`) so `#planUsageChip` renders immediately on page load/reconnect. `planUsageChipEnabled()` remains the single resolver behind the checkbox and chip visibility (DISPLAY only) — the SAME `showPlanUsageLimits` setting also doubles as the server-side telemetry COLLECTION switch, read FRESH from `settings.json` by `readPlanUsageTelemetryEnabled()` at every claude session create/respawn (`TmuxManager.createSession`/`respawnPane`), never cached, with no per-session field and no per-request wire field — applies uniformly across every claude-creation path (interactive Run, cron, Ralph Loop API, quick-start) and survives a Codeman restart by construction (nothing per-session to lose). ⚠️ An ABSENT key reads as ON, the same way an absent `workspaceHooksEnabled` does: the desktop chip already shows as on for an install that never touched the setting, and the exporter posts only to this Codeman over loopback. Resolving the default in the reader is what keeps `GET /api/settings` a plain read. It briefly reconciled the key on first read (persisting `true` when absent), but `readJsonConfig()` answers `{}` for ANY read failure, not only ENOENT, and every page load hits that route, so one unlucky read replaced the whole settings file with a one-key file; pinned by `test/routes/system-routes-settings-get-plan-usage-default.test.ts`. ⚠️ The client sends `showPlanUsageLimits` in a settings save ONLY when that save FLIPS the chip relative to what the device had (`planUsageCollectionFlip()` in settings-ui.js): the chip defaults OFF on handhelds, so sending it on every save let a phone saving its font size persist `false` and switch collection off for every desktop, whose chip then went stale with no error anywhere. An explicit toggle on any device still writes the switch. Injection covers LOCAL tmux-spawned claude sessions only: the non-tmux direct-PTY fallback (`Session.startInteractive` when tmux is unavailable) and the remote/docker pane builders do not carry the flag. Registry-gated on `getCli(mode)?.capabilities.statusLineTelemetry` rather than a hardcoded mode string. **Distinct from auto-resume** (which reacts to the Claude limit _message_; this proactively shows live percentages). Design: `docs/usage-limits-display-plan.md`. Tests: `test/usage-telemetry.test.ts`, `test/codex-plan-usage.test.ts`, `test/plan-usage-chip.test.ts`, `test/plan-usage-latest.test.ts`, `test/hooks-config.test.ts` (statusline exporter script + `readPlanUsageTelemetryEnabled`), `test/statusline-cli-flag.test.ts`.
 
 ### Cron jobs