fix: inspect native Codex plugin and hook materialization in Doctor

[HengYangDS]

Summary

Make Codex Doctor use native plugin materialization and hook configuration rather than obsolete feature and explicit-MCP assumptions. Plugin-provided servers need not appear in codex mcp list; failed native inspection is unknown, not absence. A deliberately disabled hook is reported without recommending policy override.

• Inspect native plugin details independent of marketplace, version and source directory.
• Keep plugin, explicit MCP, hook execution/trust and runtime tool-loop qualification separate.
• Preserve stdout as structured input, close stdin and bound native subprocess observations.
• Do not modify models, providers, credentials, plugin policy or hook trust.

This is one generic Doctor change rebased on official main, not the larger local indexing/admission patch stack.

Validation

• node node_modules/vitest/vitest.mjs run test/codex-doctor.test.ts test/doctor-observations.test.ts --reporter=dot: 14 passed using the existing Vitest 5.0.0 toolchain.
• node node_modules/typescript/bin/tsc --noEmit: passed with TypeScript 5.9.3.
• git diff --check: passed.
• Compatibility with package.json's declared Vitest ^3.2.4 is not yet verified; the offline 3.2.7 toolchain was unavailable. A native CLI/tool loop on this rebased branch was not run.

Configuration diagnostics are deliberately not a model/storage health or all-consumer acceptance claim.