docs: add provenance comments — what was replaced, why, what was removed

Each action.yml now documents:
- Original upstream repo (GitHub Actions)
- Why it was rewritten for self-hosted Gitea
- What was removed from the original
- Author and date

setup-go/action.yml

@@ -1,3 +1,13 @@
+# Tinqs Setup Go — replaces actions/setup-go@v5
+# Original: https://github.com/actions/setup-go (GitHub-hosted, Node.js action)
+# Why rewritten: Original uses GitHub's tool cache API and Node.js runtime — neither
+#   available on self-hosted Gitea runners. This composite action downloads Go directly
+#   from go.dev and sets GITHUB_PATH. Skips install if correct version already present
+#   (for when runner image has Go pre-baked).
+# Removed from original: tool cache, go-version-file, check-latest, cache (actions/cache dep).
+# Author: Ozan / Claude Code — 2026-05-22
+# Part of: tinqs/ci (Tinqs CI toolchain)
+
 name: 'Tinqs Setup Go'
 description: 'Install Go and configure PATH (replaces actions/setup-go)'