`5x/sweep-2.md`

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# 5x sweep 2

## Verify
6/7 — M3 still FAIL (1 JS error), all else PASS.

## Caught (root cause finally pinned)
- Sweep 1's fix was aimed at the wrong error class (no-progress guard fired). Exact M3 repro (system Chrome via executablePath, not bundled Chromium) surfaced the real error: "Failed to load resource: 404" = Chrome's automatic /favicon.ico request — no favicon existed. The 3x favicon filter only matches the error TEXT, which doesn't say "favicon", so it counts as a defect.

## Fixed
- Added an inline SVG data-URI favicon (green "a" tile) to index.html <head>. Chrome no longer requests /favicon.ico at all → no 404, no console error. (Sweep-1's fetch error handling stays — it's correct hardening regardless.)