fix(engine): ignore benign media request aborts

[miguel-heygen]

Summary

• suppress Chromium net::ERR_ABORTED diagnostics for media requests cancelled during probe/seek
• preserve real media failures and all non-media request failures
• cover Puppeteer media classification plus extension fallback, including .oga

Root cause

The capture session appended every requestfailed event to its browser diagnostic buffer. Chromium commonly aborts media requests while the probe discovers or seeks audio/video, and producer probe treated any buffered net::ERR_* line as an asset-load warning even when the final media rendered correctly.

Regression coverage

• red/green unit test for benign media aborts and real failures
• @hyperframes/engine targeted test: 20/20
• @hyperframes/engine typecheck
• producer probe-stage test: 18/18
• producer full unit lanes: 295 Vitest + all Bun lanes passed
• format, lint, diff check, pre-commit fallow/typecheck passed
• full engine suite: 887 passed; 3 pre-existing LFS HDR-fixture failures in this smudge-disabled worktree

Review

Independent review caught missing .oga fallback coverage; fixed and re-reviewed with no remaining findings.

Source feedback: https://heygen.slack.com/archives/C0BGC335AQY/p1784020062434169

Reviewer action: verify benign abort suppression does not hide real media/network failures, then approve if CI is green.