Fix Codex skill discovery cwd in Freshell panes

[danshapiro]

Summary

• Launch the Codex app-server sidecar in the requested pane cwd instead of inheriting the Freshell server cwd.
• Thread cwd through fresh and resumed Codex launch planning.
• Add focused coverage for runtime sidecar cwd and launch-planner readiness behavior.

Verification

• npm run test:vitest -- test/unit/server/coding-cli/codex-app-server/runtime.test.ts test/unit/server/coding-cli/codex-app-server/launch-planner.test.ts --run
• PORT=3356 npm run build
• Dev-proof temp server on PORT=3357 showed a /tmp Codex pane with both [Skill] entries and the GitHub [Plugin], and sidecar metadata reported wrapper cwd /tmp.

[danshapiro]

Superseded by the landed aggregate parity stack in #336. Current origin/main already launches Codex app-server sidecars in the pane cwd through CodexTerminalSidecar cwd propagation and runtime cwd normalization, so this older runtime-shape branch should not be merged separately.

[danshapiro]

Closing as superseded by #336 in the accepted parity landing sequence.