feat(cursor): support model selection

[swear01]

Summary

• add Cursor model discovery via agent --list-models and expose it through machine/session RPC + API routes
• enable Cursor model-change capability and wire Cursor model pickers in new-session and session composer UI
• apply selected Cursor model to remote turns and sync model metadata on config changes

Closes #670

Testing

• npm exec -- bun test shared/src/flavors.test.ts cli/src/modules/common/cursorModels.test.ts web/src/components/AssistantChat/modelOptions.test.ts hub/src/web/routes/sessions.test.ts hub/src/web/routes/machines.test.ts
• npm exec -- bun run typecheck
• env -u HAPI_API_URL -u CLI_API_TOKEN -u HAPI_CLI_EXECUTABLE HAPI_HOME=$(mktemp -d /tmp/hapi-test-home.XXXXXX) npm exec -- bun run test (runner integration skipped by design without test hub token)
• Manual smoke test on isolated hub/runner: Cursor model list loads and model selection works

[github-actions]

Findings

• No issues found with confidence >= 80% in the added/modified lines.

Summary

• Review mode: initial
• Reviewed the full latest diff for Cursor model discovery, RPC routing, session config application, spawn argument propagation, and web selectors. Residual risk: local test automation was unavailable in this runner because bun is not installed.

Testing

• Not run (automation): bun command not found in runner image.

HAPI Bot