fix(release): stamp mcp registry metadata for npm

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Summary

• fix the npm release job that failed after v0.1.9 by stamping MCP registry metadata to the release version before npm tests and packing

What changed

• added scripts/stamp-mcp-registry-version.mjs
• updated the release workflow to stamp server.json after npm version
• added release-script fixture coverage for the stamp path and v-prefixed version rejection

Why

• packages/npm/package.json is release-stamped during publish, but server.json remained 0.0.0-development, causing the MCP registry contract test to fail before npm publish

Validation

• make verify
• make ci-scripts-test
• make npm-package-verify
• temp-copy release sequence: npm version --no-git-tag-version 0.1.10, node scripts/stamp-mcp-registry-version.mjs 0.1.10, npm test, npm pack --dry-run
• git diff --check

Notes

• v0.1.9 GitHub release was created and verified, but npm publish failed before publication. After this merges, cut a new v0.1.10 tag instead of reusing v0.1.9.