Improve orca.yaml invalid-state UI with repair guidance

[AmethystLiang]

Summary

• Replaces the terse "fix the file format" message when orca.yaml is invalid with a structured warning card showing parse-error explanation, numbered repair steps, and the example template
• Extracts ExampleTemplateCard component to reuse the template block across both the "no file" and "invalid file" states
• Restores the structured return type on hooks.check preload API to preserve type safety at the IPC boundary
• Removes a redundant setupConfig guard in AddWorktreeDialog (the resolved decision already accounts for missing config)

Test plan

• Open Settings for a repo without orca.yaml — verify the example template card renders correctly
• Add a malformed orca.yaml to a repo — verify the warning card with numbered fixes and template appears
• Add a valid orca.yaml — verify the loaded state shows script preview as before
• Create a new worktree for a repo with/without setup hooks — verify setup decision is passed correctly