perf(worklet): rate-limit the under-run position nudge (fix stutter feedback loop)

[ahonnecke]

Problem

The urgent under-run position nudge was posted per 128-sample quantum (~344 Hz), flooding the main thread and starving the refill pump — a positive-feedback stutter loop.

Fix

Cap urgent posts to ~100 Hz via _urgentInterval. One file (assets/stretch-worklet.js), +11/-1.

main's worklet doesn't currently have this rate-limit. Low-risk, worklet-only.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Performance Improvements
  • Reduced excessive position updates during streaming interruptions.
  • Improved playback stability by rate-limiting urgent buffer refill updates, including smoother handling of the first urgent under-run after streaming begins.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 24129773-71a2-4423-9755-339ffe4dab98

📥 Commits

Reviewing files that changed from the base of the PR and between c7e17f4 and 768ef13.

📒 Files selected for processing (1)

• assets/stretch-worklet.js

🚧 Files skipped from review as they are similar to previous changes (1)

• assets/stretch-worklet.js

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📝 Walkthrough

Walkthrough

The audio worklet rate-limits urgent under-run refill position notifications, while preserving an immediate post when the stream first enters an under-run state.

Changes

Position post throttling

Layer / File(s)	Summary
Interval selection and urgent-state posting assets/stretch-worklet.js	Initializes _urgentInterval, _posAccum, and _wasUrgent; _maybePostPos uses urgent or steady-state thresholds and posts immediately when urgent state begins.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: rate-limiting urgent under-run nudges in the worklet to reduce stutter.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@assets/stretch-worklet.js`:
- Around line 345-349: Update the position-posting logic around the urgent
threshold check to track the previous urgent state and detect entry into urgent
mode. Send the first urgent notification immediately on that transition, even
when _posAccum is below _urgentInterval; continue applying _urgentInterval to
subsequent urgent posts and preserve the existing steady-state behavior.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 8db6b9db-5216-455d-951a-706f42f25659

📥 Commits

Reviewing files that changed from the base of the PR and between 7082b23 and c7e17f4.

📒 Files selected for processing (1)

• assets/stretch-worklet.js