[codex] accelerate workspace and editor flows

[alexsloan]

Summary

• add generated-only vault, fidelity, perf, unit, and headless Playwright E2E validation harnesses
• move workspace scanning to a Rust flat payload, index workspace files for quick switcher/link resolution, and virtualize sidebar rows
• reduce editor typing/save overhead with revision-based snapshots, safer dirty state, and shared editor extension setup
• restore open tabs on app restart and add Cmd/Ctrl-click support for wikilinks and external URLs, including pointer cursor affordance

Notes

This PR is intentionally based on codex/open-with-loose-files so it preserves the newer sidebar/open-with/titlebar fixes and keeps the diff focused on top of that stacked branch.

Validation

• pnpm test:ci
• cargo check
• pnpm build
• git diff --check

Local install

Built and installed locally via pnpm build:install -- --yes --skip-deps for manual testing.