[codex] Add project type selection to existing-folder onboarding

[spaceshipmike]

Summary

• let existing-folder registration use a selected user-managed project type, with core validation and broad code/workspace fallback
• update the registration dialog to load live project types while preserving local-first inspection preview/copy
• add focused core and Electron e2e coverage, plus tracked app bundle output

Checks

• npm test -- packages/core/tests/registry.test.ts
• npm run typecheck
• npm run build
• npm run build -w packages/app
• npm run test:e2e -w packages/app -- -g "renders first-run onboarding"
• npm run verify:mcp-abi
• git diff --check
• git diff --cached --check
• worker review ran git diff --check and focused core tests

Skipped verification

• full root npm test, because the changed surface was covered by focused core and Electron onboarding checks.