FrameBridge 0.3.1 community source release

CONTRIBUTING.md

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+# Contributing
+
+Original FrameBridge code and project documentation use GPL-3.0-only within [LICENSING.md](LICENSING.md). Clearly marked original blog article text uses CC-BY-SA-4.0 under [blog/LICENSING.md](blog/LICENSING.md). Contributors keep their copyrights. No automatic copyright assignment or broad contributor agreement is created here.
+
+You may use, change and redistribute the software under its applicable licenses. Private modifications and independent forks do not have to be submitted upstream. To improve an official release, propose the change through the project Git so maintainers and the community can review it.
+
+Work in a separate source checkout. Describe the problem, resulting behavior, affected version and focused validation. Keep changes reviewable, identify third-party material and retain its notices. Never include credentials, runtime profiles, private keys, cookies or unrelated personal data in an issue, recording, commit or patch.
+
+Official branches and release artifacts are maintainer-controlled. Changes enter them through review; official packages are built from identified source revisions and signed through the release process. A pull request does not itself become an official binary. See [OFFICIAL-RELEASES.md](OFFICIAL-RELEASES.md).
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+Preserve the historical RC7 installer and source evidence. New executable or payload changes require a separately identifiable build. Do not present a modified artifact as the unchanged certified RC7 release.