Fix: keep generation retryable and don't disable local actions when offline

[deepfates]

Motivation

• Users could not trigger generation or perform local actions (e.g., New Story) when the browser reported offline, and no network request or server logs were produced.
• A stale navigator.onLine check and a generation error short-circuit created a silent dead-end that prevented retries after transient failures.

Description

• Remove the navigator.onLine preflight from useTextGeneration so the client attempts the real /api/generate fetch and surfaces network failures via the existing error path (client/interface/hooks/useTextGeneration.ts).
• Stop globally disabling the A/Enter control when isOffline is true and instead disable only while a generation is actively in-flight (client/interface/Interface.tsx).
• Remove the permanent short-circuit that blocked Enter after an earlier generation error so users can retry after reconnecting (client/interface/hooks/useStoryTree.ts).
• Add an end-to-end regression that exercises offline New Story, a visible generation network failure, and a successful retry after reconnect (tests/e2e/offline-controls.e2e.ts).

Testing

• Ran lint: bun run lint, which completed successfully.
• Ran unit tests: bun test ./server ./client — full suite passed (155 tests).
• Built production bundles: bun run build — build succeeded.
• Added Playwright e2e: attempted bunx playwright test tests/e2e/offline-controls.e2e.ts but execution was blocked in this environment because Playwright’s Chromium binary could not be downloaded (CDN download returned HTTP 403), so the new e2e regression could not be executed here.

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[chatgpt-codex-connector]

Delay the success mock until after reconnect

When this e2e runs, the /api/generate route is registered before context.setOffline(true), so the offline A-button click still matches this handler and is fulfilled with the 200 SSE body from the test process instead of producing the expected fetch failure. That makes the Network error assertion time out (or at least skips the intended offline error path); register the success mock only after setOffline(false), or have the route abort while the context is offline.

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