fix: verify extension catalog admission and trusted CI delivery

[AlexMikhalev]

Problem and result

A direct Microsoft package URL can become available before the extension is indexed for installation. The release verifier now requires the exact universal prerelease catalog entry, validates its advertised download against the frozen VSIX, and retains the complete catalog response. Cursor and Windsurf get independent catalog/download receipts after Open VSX publication.

Open VSX release success additionally requires publishedWithTrustedPublishing: true; a matching manually published package cannot mask an OIDC failure. The obsolete PAT bootstrap route is removed. Existing readiness gates remain unchanged.

A new read-only workflow verifies existing immutable releases without rebuilding or publishing. It checks the public release asset digests, checksum manifest, qualification report and tag commit, then performs one selected catalog readback (or four independent checks). Fresh publication jobs retain bounded indexing retries.

Validation

• Independent review: all67 Python tests pass, including real captured catalog responses and actual ZIP/file mutations; no mocked services.
• Targeted Ruff, actionlint and git diff --check pass.
• Actual anonymous0.1.3 Microsoft catalog/download passes; Open VSX, Cursor and Windsurf correctly reject0.1.3 as absent.
• Actual0.1.0 Open VSX, Cursor and Windsurf downloads match the original released payload. Open VSX reports trusted publishing false and the new trusted-publication gate correctly refuses it.
• The Open VSX namespace claim remains open: Claiming namespace applied-knowledge-systems EclipseFdn/open-vsx.org#14179. No access/readiness changes, package version bump, tag change or asset replacement.

These are catalog/package identity checks, not new native runtime or all41-functionality claims. The README change takes effect in a future package release; existing0.1.3 bytes remain immutable.

Refs #3488 (publication tracking on Gitea).