fix(crashlytics-autotriage): remove invalid --project flag from Firebase MCP config

[stozo04]

Summary

• Removes the invalid --project flag from .github/firebase-mcp.json — firebase mcp rejects it and the server crashed immediately on startup, leaving Claude with mcp_servers[].status == "pending" and no Crashlytics tools across six consecutive triage runs on issue [Crashlytics][TEST] Phase 0 retest — real ID #87.
• Switches MCP config to use the globally installed firebase binary (already pre-installed in the workflow) instead of npx firebase-tools.
• Adds a preflight step that verifies the MCP server stays alive for 5 seconds before Claude runs, so future config regressions fail the job instead of silently producing empty triage comments.

Project context is still provided by .firebaserc (openloop-8c266) and the google-github-actions/auth env vars (GOOGLE_CLOUD_PROJECT, etc.).

Test plan

• Merge and re-run crashlytics-autotriage via workflow_dispatch on issue [Crashlytics][TEST] Phase 0 retest — real ID #87 (or a new test issue with label crashlytics-auto)
• Confirm the "Verify Firebase MCP server starts" step passes
• Confirm Claude logs show mcp_servers[].status == "connected" (not "pending")
• Confirm crashlytics_get_issue returns stack trace data for issue 10e21549f1fa9333309e4c9976a11342

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