What this PR does

Before this PR:
The typescript/no-floating-promises lint rule was disabled ("off"), allowing 608 unhandled Promise expressions across 258 files.

After this PR:
The rule is enabled ("warn") and all 608 warnings are resolved. Async operations that genuinely needed await now have it; intentional fire-and-forget calls are explicitly marked with void.

Why we need it and why it was done in this way

Floating promises silently swallow errors and can cause hard-to-debug race conditions. Enabling this rule prevents future regressions.

A two-phase approach was used:

Phase 1 — Manual review (behavior change): Identified ~10 locations inside async functions where missing await was a potential bug, and added proper await:

1. src/main/ipc.ts:

   • App_SetLaunchOnBoot handler → setAppLaunchOnBoot() is async (filesystem operations on Linux). Without await, errors were silently lost.
   • App_FlushAppData handler → cookies.flushStore() and closeAllConnections() return Promises. Without await, data flush was not guaranteed before the handler returned.

2. src/main/services/SpanCacheService.ts:

   • cleanTopic() → cleanHistoryTrace(), saveSpans(), and fs.rm() were not awaited, so cleanup could complete out of order or fail silently.
   • cleanLocalData() → Converted .then() chain to await for proper error propagation.

Phase 2 — Auto-fix (no behavior change): The remaining ~600 warnings were all in contexts where void is the correct and only fix:

• Sync contexts (React event handlers, useEffect, useCallback) — cannot await
• Fire-and-forget IPC (window.api.* from renderer) — by design
• Queue operations (queue.add() in Redux thunks) — queue manages execution internally
• Notifications (notificationService.send()) — non-critical
• Electron shell/window (shell.openExternal(), loadURL(), loadFile()) — errors handled via Electron events

The following tradeoffs were made:
Using void for fire-and-forget calls makes intent explicit but does not add error handling. This preserves existing behavior while making the code self-documenting.

The following alternatives were considered:

• Adding .catch() to all 600+ call sites — rejected because it would require deciding error handling logic for each site, and none of these were handling errors before.
• Fixing everything manually — rejected as impractical for 600+ mechanical changes with no benefit over auto-fix.

Breaking changes

None. Phase 2 (void additions) has zero runtime behavior change. Phase 1 (await additions) fixes potential bugs but does not change the happy-path behavior.

Special notes for your reviewer

Focus review on the await additions (Phase 1) as these are the only behavior changes:

• src/main/ipc.ts — 2 IPC handlers now properly await async operations
• src/main/services/SpanCacheService.ts — cleanTopic() and cleanLocalData() now properly await filesystem operations

The remaining 256 files are mechanical void additions from oxlint --fix-suggestions — spot-check a few to confirm correctness, but exhaustive review is not needed.

Checklist

• PR: The PR description is expressive enough and will help future contributors
• Code: Write code that humans can understand and Keep it simple
• Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Documentation: A user-guide update was considered and is present (link) or not required. Check this only when the PR introduces or changes a user-facing feature or behavior.
• Self-review: I have reviewed my own code (e.g., via /gh-pr-review, gh pr diff, or GitHub UI) before requesting review from others

Release note

NONE