Prepare docs for modelcontextprotocol.io (#728)

This PR reorganizes and extends the existing documentation in
preparation for publishing on https://modelcontextprotocol.io/.

The current plan is for docs to remain in this repo, and be synced to
the `modelcontextprotocol/modelcontextprotocol` whenever necessary
(e.g., accompanying a release of the registry). I have included a script
in
https://github.com/modelcontextprotocol/modelcontextprotocol/pull/1725
(`bin/pull-registry-docs.sh`) that can be run manually to perform the
sync.

If we later decide to permanently move the docs to the
`modelcontextprotocol/modelcontextprotocol` repo, that also works.

This PR puts all https://modelcontextprotocol.io/ docs into
`docs/modelcontextprotocol-io/`. Docs outside that subdirectory, such as
`docs/administration/admin-operations.md`, are intended to be accessible
solely via this repo. One major exception is the
`docs/reference/server-json/` subdirectory, which will depend on the
resolution of
https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1649.
However, I think we could address that in a follow-up PR.

---------

Co-authored-by: Adam Jones <adamj+git@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>

docs/contributing/releasing.md

@@ -0,0 +1,60 @@
+# Release Guide
+
+## Creating a Release
+
+1. **Go to GitHub**: Navigate to https://github.com/modelcontextprotocol/registry/releases
+2. **Click "Draft a new release"**
+3. **Choose a tag**: Click "Choose a tag" and type a new semantic version that follows the last one available (e.g., `v1.0.0`)
+5. **Generate notes**: Click "Generate release notes" to auto-populate the name and description
+6. **Publish**: Click "Publish release"
+
+The release workflow will automatically:
+- Build binaries for 6 platforms (Linux, macOS, Windows × amd64, arm64)
+- Create and push Docker images with `:latest` and `:X.Y.Z` tags (note: no 'v' prefix)
+- Attach all artifacts to the GitHub release
+- Generate checksums and signatures
+
+## After Release
+
+- Docker images will be available at:
+  - `ghcr.io/modelcontextprotocol/registry:latest` - Latest stable release
+  - `ghcr.io/modelcontextprotocol/registry:X.Y.Z` - Specific release version (note: no 'v' prefix)
+- Binaries can be downloaded from the GitHub release page
+
+## Deploying to Production
+
+Releases do not automatically deploy to production. To deploy a release:
+
+1. Update `mcp-registry:imageTag` in `deploy/Pulumi.gcpProd.yaml` to the desired version (e.g., `1.2.3` - note: no 'v' prefix)
+2. Commit and push the change to the `main` branch (either through a PR or by pushing directly to main)
+3. The [deploy-production.yml](../../../.github/workflows/deploy-production.yml) workflow will automatically trigger and deploy the specified version
+
+See the [deployment documentation](../../../deploy/README.md) for more details.
+
+## Staging
+
+Staging auto-deploys from `main` via [deploy-staging.yml](../../../.github/workflows/deploy-staging.yml). It always runs the latest `main` branch code.
+
+## Rollback
+
+To rollback production, update `deploy/Pulumi.gcpProd.yaml` to the previous version and push.
+
+**Note:** Rollbacks may not work as expected if the release included database migrations, since migrations are not automatically reversed.
+
+## Docker Image Tags
+
+The registry publishes different Docker image tags for different use cases:
+
+- **`:latest`** - Latest stable release (updated only on releases)
+- **`:X.Y.Z`** - Specific release versions (e.g., `:1.0.0` - note: no 'v' prefix)
+- **`:main`** - Rolling tag updated on every push to main branch (continuous deployment)
+- **`:main-YYYYMMDD-sha`** - Specific development builds from main branch
+
+**Note:** Git release tags include the 'v' prefix (e.g., `v1.0.0`), but Docker image tags follow the standard Docker convention and do not include the 'v' prefix (e.g., `1.0.0`).
+
+## Versioning
+
+We use semantic versioning (SemVer):
+- `v1.0.0` - Major release with breaking changes
+- `v1.1.0` - Minor release with new features
+- `v1.0.1` - Patch release with bug fixes