feat: publish to the MCP Registry on version tags

[mashware]

What

Set up publishing to the official MCP Registry (registry.modelcontextprotocol.io, currently in preview) so the server shows up in MCP client discovery, automated on version tags.

• server.json (repo root) — official 2025-12-11 schema, io.github.mashware/domain-memory, monorepo subfolder: packages/server, npm package with stdio transport. Validated against the official $schema (ajv) → valid.
• mcpName in packages/server/package.json — the npm package-ownership marker the registry checks; it must equal server.json's name, and does.
• Integrated into the existing release.yml (not a separate workflow): after the npm publish, it syncs server.json's version to the tag, installs mcp-publisher, authenticates via GitHub OIDC, and publishes. Reuses the id-token: write permission already present.

Notes / decisions

• README left untouched on purpose. For npm packages the ownership marker is mcpName in package.json; the mcp-name: README line is the PyPI/NuGet mechanism, so adding it here would be a non-load-bearing, confusing marker. A "available on the MCP Registry" mention makes sense after the first publish.
• No new secret / no namespace claim. The repo lives under github.com/mashware, so login github-oidc authorizes the io.github.mashware/* namespace from the OIDC token.
• Preview registry. The flow may need updates as the registry stabilises. Re-running a failed registry step for an already-published version may be rejected by the registry.

Manual steps remaining (owner)

1. (Optional) local dry-run: install mcp-publisher and run mcp-publisher publish --dry-run from the repo root.
2. First publish = the version bump we deferred: bump the three package.json + server.json to the next version and push tag vX.Y.Z. That tag publishes npm and the registry in one run.

Verification

server.json validates against the official schema; release.yml is valid YAML; workspace typecheck clean; all tests green (CLI/server/web).