fix(app): register new home projects

[Brendonovich]

Summary

• register newly added Home projects through a directory-scoped backend request
• initialize Git automatically when the selected folder is empty
• seed the resolved project ID in client state and avoid redundant registration requests
• verify instance routing persists committed Git projects with non-global IDs

Tests

• bun typecheck (packages/app)
• bun test --timeout 30000 test/server/project-init-git.test.ts test/server/httpapi-instance-context.test.ts test/project/project.test.ts (packages/opencode)
• git diff --check