Add V2 third-party edit layout support

[HANCORE-linux]

Summary

• Add V2 dynamic G:<plugin> groups for eligible third-party bar widgets.
• Persist activation, removal, region changes, same-region reorder, cross-region moves, settings, reset, and rollback through the shared bar.layout contract.
• Keep V1 reconciliation isolated from V2 and synchronize vendored bar/state copies.
• Reject malformed duplicate dynamic providers before shell-config persistence.
• Add regression coverage for V2 lifecycle, all V2 styles (full, fit, dock, notch), and duplicate entries.

PR #28 was not cherry-picked or used as an implementation source.

Validation

• Independent code review: approved; no actionable findings.
• Vendoring checks and git diff --check: passed.
• Relevant QML/config regression tests: passed.
• Controlled live matrix on the local machine and machine2 (192.168.2.128): V1 ↔ V2, notch, full, fit, dock, and V2 → Omarchy → V1 all completed successfully.
• Each live stage had one production Quickshell process, omarchy-shell shell ping: ok, no QML composition errors, and no null layout entries.
• The updated bar host was deployed to both test machines without modifying /usr/share/omarchy.

Explicit limitations

• The installed Omarchy host differs from the pinned baseline content hash, so the pinned installed-package gate remains blocked by baseline drift. This is an environment-validation limitation, not a Shibumi runtime failure.
• Both physical test machines exercised one output only. Multi-output, mixed-scale, hardware, and full visual-freeze comparison remain open acceptance gates.
• A recurring Qt portal registration warning appeared on shell restart; it did not affect ping, process count, switching, or widget persistence.