Observe browser H3 resumption on new physical connections

[cppla]

Summary

• Extend the bounded loopback-only H3 diagnostic with a sanitized TLS summary and actual physical-connection closure events; join budget-bounded observers at shutdown.
• Add real-Go-peer cold/reuse/resume, ticket-receipt, privacy/schema and shutdown coverage. Production transports, dependency pins and default profiles are unchanged.
• Record one failed collector-readiness attempt separately, followed by a separately frozen corrected experiment: one readiness check plus three Chrome trials passed, each showing cold/reused IDs followed by a different resumed connection ID. Preserve failure and evidence limitations explicitly.

Validation

• Go 1.27.2: make check passed.
• Fixture race tests passed 10 repeats and an independent 3-repeat run; vet/diff checks passed.
• Ten existing AutoCAR H3 functional test groups passed three repeats with race detection (separate evidence, not a paired browser comparison).
• Chrome 154.0.8037.95 / Playwright CLI 0.1.22: twelve HTTP 200/H3 requests, eight physical connections/closure events, saved runtime argv/version before navigation, unchanged frozen inputs and executable hashes. Named sessions and local observer stopped.
• Independent source and diagnostic-evidence reviews found no blockers.

Boundaries

Controlled headless loopback observation with a lab-specific SPKI exception; not a normal browser configuration, WAN/remote measurement, packet-capture corpus, browser-side TLS instrumentation or passive-similarity claim. No full campaign restarted, no release tag, no production transport changes. Local artifacts remain outside Git.

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