wayland/lock: abort locks on initial graphics failure

[acrogenesis]

Initial lock-surface graphics failures currently abort Quickshell and leave the session locked without an authentication UI. Cancel the lock attempt instead, following the suggestion on #1106.

Wait for the compositor's locked event before sending unlock_and_destroy, then notify QML that locked is false. Handle errors only during initial surface creation; disconnect the handler after initialization and ignore failures after manager ownership transfers during reload. This deliberately unlocks a failed initial attempt without authentication and does not add retries or recovery for later rendering failures.

Validation with Qt 6.11.2 and Clang 22:

• All-features Debug build and eight focused cases pass, including real Wayland runs with both basic and threaded render loops. Both manager-transfer regressions fail before the fix and pass afterward.
• Before the ownership checks: single/two-output EGL_BAD_ALLOC injection and the full installed Omarchy shell via omarchy-system-lock, under both render loops. Failed initialization clears the lock request; wrong passwords are rejected, correct passwords authenticate through PAM, and subsequent locking succeeds in the same process.
• Prior full offscreen suite: 9/10 pass; the existing popupwindow::moveWithParent failure remains. Formatting and lint checks for the changed test pass locally; full lint uses CI's pinned toolchain.

This is a separate alternative to #1106.