perf: visibility-gate dashboard render loop

Co-authored-by: PR0M3TH3AN <[email protected]>

src/context/CONTEXT_2026-02-16.md

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+# Context: perf-agent (2026-02-16)
+
+## Goal
+Improve app responsiveness by finding and fixing background CPU/network work.
+
+## Scope
+- Focus on "Visibility gating" for `dashboard/index.html`.
+- Run grep searches for performance patterns.
+- Ensure `INITIAL_BASELINE.md` exists.
+
+## Constraints
+- Minimal changes.
+- Safe changes only.
+- No network access to external sites.
+- Running as a simulated agent (Jules).
+
+## Assumptions
+- `dashboard/index.html` is the primary entry point for the dashboard.
+- `setInterval` in `dashboard/index.html` runs even when tab is hidden, wasting CPU.

src/decisions/DECISIONS_2026-02-16.md

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+# DECISIONS: perf-agent (2026-02-16)
+
+## Decision: Visibility Gating for Dashboard Refresh Loop
+
+- **Decision**: Modify the `setInterval` in `dashboard/index.html` to skip rendering if `document.hidden` is true.
+- **Rationale**: The dashboard currently re-renders the DOM every 30 seconds to update TTL bars, even when the tab is in the background. This wastes CPU cycles.
+- **Consequences**:
+  - Reduced CPU usage when tab is hidden.
+  - UI might be slightly stale when tab becomes visible, so we add a `visibilitychange` listener to force an immediate update.
+
+## Alternatives Considered
+- Remove the interval entirely: Would stop updates.
+- Use `requestAnimationFrame`: Still runs (sometimes throttled) and more complex to manage with 30s intervals.
+
+## Follow-ups
+- Monitor if users complain about stale data (should be mitigated by `visibilitychange`).

src/test_logs/TEST_LOG_2026-02-16.md

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+# TEST LOG: perf-agent (2026-02-16)
+
+## Verification Steps
+
+1. **Static Analysis**: Verify `dashboard/index.html` contains `document.hidden` check inside `setInterval`.
+2. **Static Analysis**: Verify `dashboard/index.html` contains `document.addEventListener('visibilitychange', ...)` handler.
+3. **Linting**: Run `npm run lint` to ensure no syntax errors or style violations.
+
+## Results
+
+- [x] Static Analysis (Hidden Check): Passed (Verified in `dashboard/index.html`)
+- [x] Static Analysis (Visibility Listener): Passed (Verified in `dashboard/index.html`)
+- [ ] Linting: Scheduled for Scheduler Completion step.

src/todo/TODO_2026-02-16.md

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+# TODO: perf-agent (2026-02-16)
+
+- [ ] Create context file.
+- [ ] Run grep searches.
+- [ ] Create hits file.
+- [ ] Implement visibility gating in `dashboard/index.html`.
+- [ ] Document decisions.
+- [ ] Create test logs.
+- [ ] Create daily report.
+- [ ] Commit and push.