test(lease): assert promotion wiring against composed base+overlay template

The lease-overlay split (a42d5e2e) moved the promotion hooks out of the
base Claude settings template; the wiring test still read the base alone
and failed on the absent UserPromptSubmit event, stopping the whole
test:framework-shell chain. The test now composes base + lease overlay
the way a launched seat does (hook event arrays concatenate, base
first) and asserts the same wiring contract against that view.

Reported-by: goals (clean-head probe on 5e154310)

packages/mosaic/src/lease-broker/promotion_trigger_unittest.py

@@ -23,6 +23,7 @@ COMPLETE_PATH = TOOLS / "promote-complete.py"
 OBSERVER_CLIENT_PATH = TOOLS / "receipt-observer-client.py"
 RECEIPT_CHALLENGE_PATH = TOOLS / "receipt_challenge.py"
 CLAUDE_SETTINGS = FRAMEWORK / "runtime/claude/settings.json"
+CLAUDE_LEASE_OVERLAY = FRAMEWORK / "runtime/claude/lease-overlay.json"
 CLAUDE_COMMAND = FRAMEWORK / "runtime/claude/commands/mosaic-promote.md"
 SESSION_ID = "a" * 64
 CHALLENGE = "b" * 64
@@ -569,8 +570,15 @@ class PromotionCompleteTest(PromotionHookFixture):
 
 class PromotionTemplateWiringTest(unittest.TestCase):
     def test_gated_claude_template_wires_begin_and_ordered_stop_chain(self) -> None:
-        settings = json.loads(CLAUDE_SETTINGS.read_text(encoding="utf-8"))
-        hooks = settings["hooks"]
+        base = json.loads(CLAUDE_SETTINGS.read_text(encoding="utf-8"))
+        overlay = json.loads(CLAUDE_LEASE_OVERLAY.read_text(encoding="utf-8"))
+        # A launched seat composes base + lease overlay; hook event arrays
+        # concatenate with base entries first, so wiring is asserted against
+        # the composed view rather than either file alone.
+        hooks: dict[str, list] = {}
+        for layer in (base["hooks"], overlay["hooks"]):
+            for event, groups in layer.items():
+                hooks.setdefault(event, []).extend(groups)
         submit_commands = [
             hook["command"]
             for group in hooks["UserPromptSubmit"]