Add monthly manual versioning (major.minor VERSION + release workflow) (#88)

* Add monthly manual versioning: VERSION file + release-version workflow

* Version as major.minor (1.0); bump minor monthly, major for breaking

* Clarify BCQuality minor is monotonic and never resets across major bumps

* Align comment with engine X.Y.Z scheme (minor = Z)

* Document BCQuality versioning in README

* Drop PRReviewAgent reference from README versioning section

* Derive release version from git tags, drop VERSION file

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Co-authored-by: wenjiefan <wenjiefan@microsoft.com>

README.md

@@ -136,6 +136,18 @@ For the end-to-end flow — from orchestrator trigger through to how output reac
 │   └── /skills/
 ```
 
+## Versioning
+
+BCQuality content is released on demand — roughly monthly, not on every commit. A
+release is a `major.minor` value derived from git tags, cut manually via the
+`Release version` workflow: pick whether to bump the minor or the major, and it
+computes the next version and tags the current `main` as `v{major}.{minor}`.
+
+- Bump the **minor** for the usual periodic content update; bump the **major**
+  only for a breaking change.
+- The minor is a **monotonic counter** — it only ever increments and never
+  resets, even across a major bump — so it uniquely identifies a release.
+
 ## Contributing
 
 Contributions are welcome. Before submitting a PR: