test(mcp): clean daemon registry after forced teardown

[danusha2345]

Summary

mcp-daemon.test.ts deliberately SIGKILLs detached daemons during cleanup. That bypasses Daemon.stop() and therefore deregisterDaemon(), leaving one dead JSON record per test under ~/.codegraph/daemons after every suite run.

• explicitly deregister the temporary project after the forced teardown
• keep the production daemon lifecycle unchanged
• prevent repeated local and CI runs from accumulating dead discovery records

Verification

• npm run build
• npx vitest run __tests__/mcp-daemon.test.ts --reporter=dot — 10 passed
• registry count stayed 0 -> 0 across the focused suite
• full integration suite with the same commit — 198 files, 3283 passed, 10 skipped; registry count remained unchanged