fix(docking): retry the undock; a lost keyword left the panel black

Round 6 passed on the plug side but unplugging the cable left the laptop
panel black until it was re-docked. The journal named it: across three
undocks, two logged result=enable-timeout and one result=ok — a race, not
a logic error.

Two halves, both needed:

  - `hyprctl keyword monitor eDP-1,preferred,auto,1` is accepted (exit 0)
    while Hyprland is still tearing down the departing external, then
    silently dropped. Re-issue it on every poll for 5s and keep `monitors`
    listing the panel — not hyprctl's exit code — as the only proof.

  - The watcher fired the undock once off the removal event and marked the
    departure handled regardless (`|| true` + awaiting_lid_open=1). Since
    known_outputs had already moved, the set-changed guard never reopened
    and nothing retried, so one lost keyword cost the panel until re-dock.
    The undock is now a queued invariant driven on the 1s tick, bounded at
    6 attempts so a genuinely unenableable panel can't pin the inhibitor.

The VM harness cannot reach this race: QEMU's headless backend aborts
Hyprland if the last active output is deleted while the DRM output is
disabled, so the test must undock before removing DP-1 and never collides
the two. Noted there, and V3 queued as round 7 — unplug 5+ times, since
the old failure only hit ~2 in 3.

Verified: V2 — nix flake check --no-build; monitor-fallback.nix exit 0 in
57s; shellcheck clean. The fix itself is V3 pending.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tools/monitor-fallback.nix

@@ -130,6 +130,13 @@ pkgs.testers.runNixOSTest {
     # monitorremoved event still proves that the watcher retains the inhibitor
     # until lid-open, without mistaking a backend limitation for product
     # behavior.  Physical cable-yank timing remains the bounded V3 check.
+    #
+    # Undocking a quiescent output is therefore all this harness can assert —
+    # and that gap is exactly what shipped a black panel in round 6: on real
+    # hardware the enable collides with the departing external's teardown and
+    # is silently dropped ~2 times in 3.  The keyword re-issue in the
+    # transition and the tick-driven retry in the watcher are what cover it;
+    # neither is exercised below, so do not read a pass here as proof of them.
     user(f"{transition} undock Virtual-1")
     machine.wait_until_succeeds(
         hy + "-j monitors' | jq -e 'any(.[]; .name == \"Virtual-1\")'", timeout=20