test: v0.2.0 multi-active + layout-slot assertions

Add 42 new assertions covering: bw-compat register without opts,
multi-active open(A)+open(B) leaving both open, per-id close(id),
bw-compat close()/is_open() operating on the focused panel, layout-
slot resolution (left-half / right-half / center default / custom-fn),
Loud-Error on unknown slot name, hit-test dispatch against window
bounds with reverse open-order, is_pausing scanning all open windows.

Existing 12 baseline assertions retained and still pass via the bw-
compat shim. Total 54 pass / 0 fail.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

manifest.lib

@@ -1,9 +1,9 @@
 {
     "id": "lib-core.panel-test",
     "role": "test",
-    "version": "0.1.0",
+    "version": "0.2.0",
     "api_min": "0.1",
     "deps": [
-        {"id": "lib-core.panel", "version": "0.1.1"}
+        {"id": "lib-core.panel", "version": "0.2.0"}
     ]
 }