[codex] Generalize sparse agent worktree inference

[jamesrochabrun]

Summary

Generalizes AgentHub's sparse checkout inference for launched agent worktrees so monorepo subdirectory starts no longer depend on hard-coded paths like ios, android, ribbons, or tools/ios/SproutApp.

The new flow infers a sparse owner path from project markers near startPath, keeps repo-root launches as full checkouts, preserves explicit sparseProfile and fullCheckout, and includes tracked support paths such as .agents, .claude, and git hook support when present. Gradle support is included only when a Gradle marker is detected.

Why

The previous implementation solved sparse checkout for one set of known monorepo layouts, but it did not cover generic layouts like apps/ios and apps/android. That meant AgentHub could still materialize an entire monorepo when the desired agent launch path was only one app subtree.

Validation

• swift test --filter WorktreeManagementServiceTests passed.
• ./scripts/test.sh passed the fast package gates through AgentHubCLI, AgentHubGitHub, SimulatorPreview, and Storybook.
• Full ./scripts/test.sh is not green due to unrelated AgentHubCore issues observed before PR creation:
  • DiffAvailabilityServiceTests: Invalidate succeeds after the adaptive window elapses expectation failure.
  • WebPreviewResolverLaunchOptionsTests: Has no static fallback when no HTML files exist timed out.
  • CodeEdit dependency SwiftLint plugin phases reported 0 violations but failed with The folder “Output” doesn’t exist.