test(mcp): hash outputDir into PLAYWRIGHT_SOCKETS_DIR

[Copilot]

Concurrent test runs from two Playwright checkouts share PLAYWRIGHT_SOCKETS_DIR (currently <tmpdir>/ds<workerIndex>) and collide. Within a single checkout we want collisions preserved to surface races and cleanup bugs.

Change

• In tests/mcp/cli-fixtures.ts, append a short SHA1 hash of test.info().outputDir to the socket dir name.
• Hash truncated to 8 hex chars to stay well under UNIX domain socket path length limits (~104 bytes on macOS).

PLAYWRIGHT_SOCKETS_DIR: path.join(
  os.tmpdir(),
  'ds' + String(test.info().workerIndex) + '-' +
    crypto.createHash('sha1').update(test.info().outputDir).digest('hex').slice(0, 8),
),

outputDir is stable for a given test within a checkout (collisions retained) and differs across checkouts (isolation achieved).