Handle missing Codex rate limits via app-server fallback

[smoochy]

Summary

• add a local codex app-server fallback for rate limits when newer token_count events omit rate_limits
• fall back to the most recent session snapshot with rate_limits if the app-server path is unavailable
• show the active rate-limit source in the tooltip, details view, and optionally in the status bar
• add explicit log levels (debug, info, warn, error) plus clearer source-switch logging
• prefer bundled Codex executables before codex on PATH and avoid noisy per-candidate failure logs when a later candidate succeeds
• add a packaging helper that writes codex-ratelimit-<version>.vsix
• update the README and changelog to document the new behavior

Display

Status Bar

Mouse-over in Status Bar

Details view

Testing

• npm run compile
• npm run package:vsix
• manual validation in VS Code against local Codex session data, including app-server fallback and source display

Note

All code, documentation, and packaging changes in this PR were created with AI assistance.