fix(renderer): recover from bounded process failures

[luoye520ww]

Summary

Add bounded renderer-process recovery for the white-screen failure tracked by #885.

Changes

• Handle Electron render-process-gone and unresponsive events in the main process.
• Reload at most three times inside a five-minute window with a short delay.
• Ignore clean exits, deduplicate concurrent failures, cancel pending reloads when the renderer responds or finishes loading, and stop retrying after the budget is exhausted.
• Keep the policy and reducer pure/testable; only the small BrowserWindow adapter owns timers and reload side effects.

Part of #885. This is intentionally separate from the React ErrorBoundary and Kun runtime lifecycle PRs.

Tests

• npm.cmd exec vitest run src/main/renderer-process-recovery.test.ts
• npm.cmd run typecheck
• npm.cmd run lint -- --quiet
• npm.cmd run build
• git diff --check

[luoye520ww]

Superseded by consolidated runtime recovery PR #947, which passed Typecheck, Linux, macOS, and Windows packaged checks. Closing this duplicate to keep the review surface focused.