This commit introduces fail-fast error handling for config loading failures,
replacing the previous silent fallback to default config which could cause
data loss (e.g., all user providers disappearing).
Key changes:
Backend (Rust):
- Replace AppState::new() with AppState::try_new() to explicitly propagate errors
- Remove Default trait to prevent accidental empty state creation
- Add init_status module as global error cache (OnceLock + RwLock)
- Implement dual-channel error notification:
1. Event emission (low-latency, may race with frontend subscription)
2. Command-based polling (reliable, guaranteed delivery)
- Remove unconditional save on startup to prevent overwriting corrupted config
Frontend (TypeScript):
- Add event listener for "configLoadError" (fast path)
- Add bootstrap-time polling via get_init_error command (reliable path)
- Display detailed error dialog with recovery instructions
- Prompt user to exit for manual repair
Impact:
- First-time users: No change (load() returns Ok(default) when file missing)
- Corrupted config: Application shows error and exits gracefully
- Prevents accidental config overwrite during initialization
Fixes the only critical issue identified in previous code review (silent
fallback causing data loss).
