fix: stabilize refresh performance for v2.2.1 - #78

Summary

• Mitigates Linux/high-history CPU load by honoring the configured polling interval, quiet-debouncing file watches, bounding timestamp probes, reusing one manifest per refresh, and coalescing concurrent triggers.
• Adds anonymous stage diagnostics while preserving the previous snapshot on incomplete scans or reads.
• Builds on the fixes already merged through contributor PR fix: stop treating daily dates on the 1st as month-only labels #71 and maintainer PR fix: default @ccu-bot to English replies #72, adding focused regression tests, testable date-label helpers, Codex repository guidance, truthful automation attribution, and tag-safe publish retries.

Contributor history

• fix: stop treating daily dates on the 1st as month-only labels #71 was merged through @YuboZhang's original PR and is the credited foundation for the first-of-month and negative-UTC date-label fixes.
• fix: default @ccu-bot to English replies #72 was reduced to its independent English-default automation fix and merged through its original PR.
• This PR now merges the resulting main history and contains only the V2.2.1 follow-up refactoring, tests, performance mitigation, diagnostics, policy, and automation hardening.

Linked issues

Fixes for #54 are merged through #71. Relates to #70; keep #70 open until Linux validation is confirmed.

Type of change

• Bug fix (non-breaking) → fix (patch)

How was this tested?

• TypeScript compile succeeded.
• 166 automated tests: 165 passed, 0 failed, 1 filesystem-dependent identity fixture skipped.
• VSCE package inspection confirmed the VSIX contains no source, tests, agent state, secrets, or source maps.
• GrowthJack.claude-code-usage@2.2.1 installed successfully into an isolated VS Code profile on macOS.
• Linux validation remains the close gate for Extension causes high cpu load #70.

Checklist

• Contributor fixes retain their original merged PR attribution
• npm run compile equivalent is clean
• All seven UI locales remain complete
• All six README editions updated together
• CHANGELOG.md updated
• New refresh choices preserve the existing 2-second default
• No new runtime dependencies

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