Fix standalone Proxy release pipeline and publish 0.9.2

[antoinezambelli]

Summary

Forge 0.9.1 introduced the standalone Proxy distribution, but its release
pipeline attempted critical artifact work after merge and did not successfully
publish the platform binaries.

This PR releases 0.9.2 as a packaging-only correction. It does not change
Forge’s forwarding, routing, backend, or guardrail behavior.

Changes

• Build final Proxy artifacts in the release pull request.
• Run three independent Proxy platform jobs—Windows x64, Linux x64/glibc, and
  macOS ARM64—followed by a fourth aggregation-only job.
• Build each artifact through its documented platform entrypoint:
  • build_windows.ps1
  • build_macos.sh
  • the Linux Dockerfile
• Build the Linux artifact with Python 3.14 in the Ubuntu 24.04 compatibility
  image, then exercise those exact bytes on Ubuntu 24.04, Debian 13, and Fedora 43.
• Retain one verified publication bundle containing the exact PR-tested bytes.
• Make post-merge publication download and promote that bundle without
  rebuilding or repeating lifecycle tests.
• Bind the retained candidate to the release version and Git source tree.
• Capture uploaded GitHub asset IDs directly for accurate rollback.
• Bump Forge and the standalone Proxy pointer to 0.9.2.

Ordinary Forge pull requests remain unaffected: Proxy candidate CI runs only
when installer/proxy-stable.txt changes.

Validation

• Full test suite on Python 3.12, 3.13, and 3.14: 1,537 passed on each version.
• Native candidate builds and lifecycle checks passed on Windows x64, Linux
  x64/glibc, and macOS ARM64.
• The exact Linux candidate passed runtime validation on Ubuntu 24.04,
  Debian 13, and Fedora 43.
• The aggregation job verified and retained the final publication bundle.
• All seven required GitHub Actions checks passed.
• Two read-only reviews of the final artifact and publication flow found no
  merge blocker.

Authored by Codex; human reviewed.