chore: fix FileVersion warning and add RELEASING.md

- Remove FileVersion from pack-version command as it only accepts
  numeric versions (e.g., 5.0.0.0), not semver with prerelease tags
- Add RELEASING.md documenting the release process and version sync

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: dbrattli

RELEASING.md

@@ -0,0 +1,77 @@
+# Releasing Fable.Python
+
+This document describes the release process for Fable.Python and how to keep versions in sync with Fable.
+
+## Version Synchronization with Fable
+
+Fable.Python versions should stay in sync with Fable. For example, if Fable releases `5.0.0-alpha.20`, Fable.Python should release `5.0.0-alpha.20`.
+
+## Release Process
+
+This project uses [release-please](https://github.com/googleapis/release-please) to automate releases. Release-please creates and maintains a release PR that updates automatically as commits are merged to main.
+
+### Standard Release
+
+When the Fable.Python version naturally aligns with Fable (no version override needed):
+
+1. Merge the release-please PR
+2. The GitHub Action will create a release and tag
+
+### Forcing a Specific Version
+
+When release-please calculates a different version than Fable (e.g., due to `feat:` commits bumping the minor version), you need to override it:
+
+1. Add `release-as` to `release-please-config.json`:
+
+```json
+{
+  "packages": {
+    ".": {
+      "release-type": "simple",
+      "release-as": "5.0.0-alpha.20",
+      ...
+    }
+  }
+}
+```
+
+2. Update `.release-please-manifest.json` if needed:
+
+```json
+{
+  ".": "5.0.0-alpha.19"
+}
+```
+
+The manifest represents the *current* released version. Release-please uses this as the baseline.
+
+3. Commit and push to main (or create a PR)
+
+4. Release-please will update its PR to use the specified version
+
+5. **Important**: After the release, remove `release-as` from the config so future releases calculate versions normally
+
+### Hotfix Releases
+
+If you need to release a fix after syncing with Fable (e.g., a bug found in `5.0.0-alpha.20`):
+
+Use the format `5.0.0-alpha.20.1`, `5.0.0-alpha.20.2`, etc. This:
+
+- Clearly shows the relationship to the base version
+- Sorts correctly in package managers
+- Resets when the next Fable version is released
+
+## Configuration Files
+
+- `release-please-config.json` - Release-please configuration (release type, version overrides, extra files to update)
+- `.release-please-manifest.json` - Tracks the current released version
+
+## Conventional Commits
+
+Release-please uses [conventional commits](https://www.conventionalcommits.org/) to determine version bumps:
+
+- `feat:` - Bumps minor version (in pre-major, due to `bump-minor-pre-major: true`)
+- `fix:` - Bumps patch version
+- `chore:`, `docs:`, `style:`, `refactor:`, `test:` - No version bump
+
+When syncing with Fable, the automatic version calculation may not match Fable's version, which is why `release-as` is sometimes needed.

justfile

@@ -65,8 +65,9 @@ pack: build
     dotnet pack {{src_path}} -c Release
 
 # Create NuGet package with specific version (used in CI)
+# Note: FileVersion must be numeric-only (e.g., 5.0.0.0), so we don't set it for prerelease versions
 pack-version version:
-    dotnet pack {{src_path}} -c Release -p:PackageVersion={{version}} -p:FileVersion={{version}} -p:InformationalVersion={{version}}
+    dotnet pack {{src_path}} -c Release -p:PackageVersion={{version}} -p:InformationalVersion={{version}}
 
 # Format code with Fantomas
 format: