fix(desktop): preserve generation timeout reason and raise dropdown ceiling

[hqhq1025]

Fixes #164.

Summary

• Root cause of the opaque "Request was aborted." message. When the generation timer fires, armGenerationTimeout calls controller.abort(new CodesignError('Generation aborted after {n}s (Settings → Advanced → Generation timeout).', 'GENERATION_TIMEOUT')). But the Anthropic and OpenAI SDKs catch the aborted fetch and rethrow their own generic 'Request was aborted.', which drops signal.reason. The main-process catch then logged and re-threw that opaque error, so the user never saw the configured timeout or where to change it.
• Fix at the catch boundary, not the SDK boundary. New extractGenerationTimeoutError(signal) reads back the CodesignError we stashed. Both codesign:v1:generate and the legacy codesign:generate catch blocks now prefer it over the rewritten SDK error, so the log row and the renderer toast both carry GENERATION_TIMEOUT with the full message.
• Settings dropdown ceiling raised. The default preference is 1200s (20 min) but the UI only listed 60/120/180/300, so the select rendered blank and updatePref silently downgraded on save (covered in project_bug_settings_timeout_dropdown memory — this PR resolves that). Options now run 60s / 2m / 3m / 5m / 10m / 20m / 30m / 1h / 2h, and a stored value outside the list is injected so the user's existing choice is preserved.

Changes

• apps/desktop/src/main/generation-ipc.ts — export extractGenerationTimeoutError(signal).
• apps/desktop/src/main/index.ts — both generate catch blocks upgrade the SDK error back to GENERATION_TIMEOUT when our timer fired.
• apps/desktop/src/renderer/src/components/Settings.tsx — TIMEOUT_OPTION_SECONDS + resolveTimeoutOptions(currentSec) helper; dropdown maps from it.
• Tests: new extractGenerationTimeoutError suite (4 cases) + resolveTimeoutOptions suite (4 cases).
• Changeset: patch.

PRINCIPLES §5b

• Compatibility: prefs schema unchanged, only the list of UI choices widened. Any stored timeout (including the legacy 1200) renders correctly.
• Upgradeability: resolveTimeoutOptions merges unknown stored values, so we can change the canonical list in the future without stranding user settings.
• No bloat: one new exported function per concern, no new deps.
• Elegance: fix is at the one place where the SDK's rewrite lands (the catch), not spread across every provider adapter.

Test plan

• pnpm typecheck — 10/10 tasks pass.
• pnpm --filter @open-codesign/desktop test -- --run — 878/878 pass.
• pnpm lint — clean.
• Full pre-commit hook (turbo full test + lint) — clean.
• Manual: Settings → Advanced shows the new 30m/1h/2h choices; stored 1200s renders as "1200 s"; changing to 3600s and triggering a generation that exceeds the provider turn time shows the friendly GENERATION_TIMEOUT toast instead of "Request was aborted."

Coordination

• Does not touch retry.ts or remapProviderError (out of scope, other PRs own those).
• Does not change applyGenerateError in the renderer store — the richer error code already flows through the normal error pipeline; a follow-up can add a "Open Settings" secondary action on the toast if desired.

😇

[github-actions]

Findings

• None.

Summary

• Review mode: initial
• No issues were identified on added/modified lines in this diff at high confidence.
• Residual risk: docs/VISION.md and docs/PRINCIPLES.md were not found in this checkout (Not found in repo/docs), so architectural/principle alignment could only be checked against CLAUDE.md and the changed code/tests.

Testing

• Not run (automation)

open-codesign Bot