Remove installed overlays tier to enforce clean separation of concerns:
- workflow add installs workflows only (no overlay copying)
- workflow overlay add installs overlays only (project-local)
Changes:
- Remove InstalledOverlaySource class and all references
- Remove overlay-copying logic from _validate_and_install_local()
- Update WorkflowResolver to 2-tier: project overlays + base workflow
- Fix --priority override timing: apply before validation, not after
- Remove tests for installed overlays (no longer applicable)
Rationale: If upstream controls both base workflow and shipped overlays,
and both get overwritten on bundle update, there's no reason to ship
overlays separately. Overlays only make sense when someone other than
the base author adds them.
Resolves all three review findings from PR #3557:
- r3594064677: workflow add no longer copies overlays from all call sites
- r3594064705: --priority override now applied before validation
- r3594064726: no stale installed overlays (tier removed entirely)
Assisted-by: Claude (model: claude-opus-4-7, autonomous)
cc281856d6