feat: ship .mcp.json with scaffolded projects (#55)

[hifi-phil]

Summary

• Add template/.mcp.json so every scaffolded project is immediately testable in Claude Code after init + discover + npm run build — no manual claude mcp add required
• Update template/README.md with a "Testing with Claude Code" section describing the full setup flow
• Update template/CLAUDE.md to reference .mcp.json in the testing section
• Update root CLAUDE.md to note that scaffolded projects ship with .mcp.json
• Extend packages/create-mcp-server/src/scaffold.ts next-steps output to include discover, build, and claude . steps pointing users at Claude Code
• Add a scaffold unit test asserting .mcp.json is emitted into every new project
• Update the template-structure snapshot to include .mcp.json in the file listing

Design decision: Option 2 — node --env-file=.env ./dist/index.js

.mcp.json uses the Node.js 22 --env-file flag to load credentials at startup:

{
  "mcpServers": {
    "umbraco": {
      "command": "node",
      "args": ["--env-file=.env", "./dist/index.js"]
    }
  }
}

Rationale: .env is already gitignored by the template and populated by init. Inlining credentials in .mcp.json (option 1 / example file approach) would either require an extra init step to write the real file or leave secrets in git. With --env-file=.env the committed file is always safe, init writes exactly one file (.env, which it was already doing), and there is no .mcp.json.example / .mcp.json duplication to confuse users. Node.js 22 is the minimum runtime required by the template, so --env-file is always available.

NODE_TLS_REJECT_UNAUTHORIZED=0 is already in .env.example (and therefore in the .env that init produces), so local HTTPS with self-signed certs works out of the box.

Test commands run

Command	Result
npm install	✅ pass
npm run build	✅ pass
npm run test	✅ 456 tests passed (479 total incl. stdio suite)
npm test -w packages/hosted-mcp	✅ 191 tests passed
npm run build -w packages/create-mcp-server	✅ pass (copies template to dist/)
npm test -w packages/create-mcp-server	✅ 122 tests passed (up from 121; new .mcp.json test added)
npm run build -w template	✅ pass
npm run test:template	✅ 24 tests passed

Tests skipped and why

Command	Reason skipped
npm run test:cli	Requires a running Umbraco instance (dotnet run) — not available in this env
npm run test:integration / test:integration:chained	Requires Wrangler + running worker — not available
npm run test:e2e / test:e2e:chained	Requires Playwright + running Umbraco instance — not available
npm run test:cli:evals	Requires ANTHROPIC_API_KEY or Claude Code subscription
TEST_SQL_CONNECTION_STRING=... npm run test:e2e -w packages/create-mcp-server	Requires SQL Server + .NET 10 — not available

Conflict note

Issue #52 (unify init around {url, username, password}) is in flight in parallel. That PR will change how init populates .env. The .mcp.json added here is unaffected by that change — both options write the same credentials to .env. No resolution needed here; whichever PR lands second will not conflict on .mcp.json itself.

Closes #55