Restore current GitHub Actions outputs and reproducible Docker builds

[guilhem]

Restore GitHub environment-file outputs through the current Actions SDK, patch the HTML parser, and update the GitHub client to remove its legacy OpenPGP dependency. Build the action from its selected Git reference instead of always running the 0.5.2 image. Simplify the static Docker build and update CI so pull requests build without publishing.

Add a mocked feed/API regression check covering authentication, labels, duplicate detection, individual issues, aggregation, dry-run and GITHUB_OUTPUT.

Validation: Go tests, vet, actionlint, vulnerability scanning and static amd64/arm64 compilation passed locally. No vulnerabilities were found. Docker build verification runs on the PR; no live issue creation or GHCR publication was performed during local validation. The existing first-page deduplication and aggregation limits are documented.

Fixes #42.

[github-advanced-security]

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[guilhem]

@codex review

Please review HEAD 6cee756c4ef88d313ceb7b9861127842f8c5e35c.

Objective: restore a useful dormant tool with supported builds and correct runtime behavior.
Scope: GitHub environment-file outputs, current GitHub/HTML dependencies, selected-reference Dockerfile action builds, feed/API regression tests and CI.
Watch for: authentication, duplicate detection/aggregation/output semantics, runner-owned output files and no image publishing from pull requests.
Validation: local tests, vet, actionlint and vulnerability scanning passed; mocked feed/API tests and static amd64/arm64 builds passed. Independent read-only acceptance review found no blocking defect. GitHub CI is pending; no live publication claimed.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-02T03:43:13.519822Z	6cee756	Manual request

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Nice work!

Reviewed commit: 6cee756c4e

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".