Improve Codex spawn failure diagnostics

[danshapiro]

Summary

• attach retryable spawn diagnostics to Codex app server startup failures
• add bounded process and sidecar metadata probes for EAGAIN/EMFILE/ENFILE/ENOMEM launch failures
• include launch, process, and registry diagnostics in terminal.create structured logs without changing the WebSocket protocol

Verification

• npm run test:vitest -- run test/unit/server/coding-cli/codex-app-server/runtime.test.ts test/server/ws-protocol.test.ts --config vitest.server.config.ts
• git diff --check HEAD

Known pre-existing issue: broad npm run check was observed failing intermittently in FreshAgentView keyboard scroll tests on main-era code; this is being stabilized in the follow-up branch requested by the user.