fix(bar): skip V1 reconciliation in V2 mode

[Deoxizn]

Summary

Skip reconcileV1PluginGroups when the shell is using the V2 layout.

V1 reconciliation rewrites bar.layout with V1-only group assignments, which removes any V2 layout state and leaves third-party plugins unable to enable or disable themselves from the control center.

This fix guards the three call sites in Bar.qml where reconcileV1PluginGroups is invoked:

• The install/uninstall flow (around line 826)
• The rollback path in the same flow (around line 864)
• applyProviderLayoutTransaction (around line 885 + rollback at 895)

In V2 mode, the reconciliation is skipped so the V2 layout is preserved.

Additional fix

Updated the ControlCenterPanel error message to show a V2-specific hint when plugin activation fails in V2 mode, instead of always suggesting V1-only guidance.

[HANCORE-linux]

Closing this PR as superseded by PR #32.

PR #28 addressed one narrow V1/V2 defect by guarding three V1 reconciliation call sites. It did not cover the complete Step 1C contract: startup/timer reconciliation isolation, V2 dynamic G:<plugin> groups for eligible third-party providers, entry-point validation, activation/removal, requested-region changes, same-region reorder, cross-region moves, settings preservation, transactional rollback, shared bar.layout synchronization, or the required style/lifecycle regression coverage.

The Step 1C implementation in PR #32 provides those behaviors, includes the vendored copies and regression tests, and was independently reviewed and validated in live matrices on the local machine and machine2. PR #28 was not cherry-picked or used as an implementation source.