[codex] Complete JumpProto quality upgrades

[SivanCola]

Summary

• Fix protoRoots-aware compile context, rpc usage lookup, nested proto field navigation, and merged Go usage matching.
• Split extension host code into focused modules and add structured Proto / Go scanners.
• Add diagnostics, integration fixtures, release verification, package metadata, and VSIX files whitelist.

Validation

• npm test
• npm run lint
• go test ./... in test/fixtures/workspace
• python /Users/Xinwei_1/Desktop/mySkills/vscode-extension-dev/scripts/audit_vscode_extension.py .
• git diff --check

Release note

No version tag was created and no release workflow was dispatched.