feat(869-c4): activation version-coupling assertion (Part of #869)

Part of #869

Mos (id-11) Gate-16 merge: independent APPROVE @90eb48fa (fail-closed identity locks byte-unchanged verified), author id2 != approver id11, clean mosaic-coder author, CI green wp1992. #869 Point-1 CODE COMPLETE (C1/C3/C5/C2/C4).

Co-authored-by: jason.woltje <jason@diversecanvas.com>
Co-committed-by: jason.woltje <jason@diversecanvas.com>

packages/mosaic/framework/tools/lease-broker/launch-runtime.py

@@ -12,11 +12,24 @@ from collections.abc import Callable, Mapping, Sequence
 from pathlib import Path
 from typing import Final
 
+from activation_version_gate import (
+    EXPECTED_ACTIVATION_CAPABILITY,
+    ActivationCapability,
+    VersionCouplingError,
+    assert_activation_capability_matches,
+    default_probe_activation_capability,
+)
 from lease_generation import initialize_runtime_generation
 
 MAX_FRAME: Final = 64 * 1024
 BROKER_TIMEOUT_SECONDS: Final = 1.5
 CLAUDE_DANGEROUS_FLAG: Final = "--dangerously-skip-permissions"
+# Distinct, non-overlapping exit code for the C4 version-coupling gate (see
+# `activation_version_gate.py`) — deliberately different from the `1`
+# (broker registration failed closed) and `64` (usage error) codes already
+# owned by this script, so a version-skew denial is unambiguous in caller
+# logs/tests and is never confused with a broker-availability failure.
+EXIT_VERSION_SKEW: Final = 65
 
 
 def broker_request(socket_path: Path, request: dict[str, object]) -> dict[str, object]:
@@ -47,6 +60,10 @@ def main(
     request: Callable[[Path, dict[str, object]], dict[str, object]] = broker_request,
     execute: Callable[[str, list[str], dict[str, str]], object] = os.execvpe,
     initialize_generation: Callable[[Path, int], None] = initialize_runtime_generation,
+    probe_activation_capability: Callable[
+        [Mapping[str, str]], ActivationCapability | None
+    ] = default_probe_activation_capability,
+    expected_activation_capability: ActivationCapability = EXPECTED_ACTIVATION_CAPABILITY,
 ) -> int:
     parser = argparse.ArgumentParser()
     parser.add_argument("--runtime", required=True, choices=("claude", "pi"))
@@ -66,6 +83,25 @@ def main(
         command = [command[0], CLAUDE_DANGEROUS_FLAG, *command[1:]]
 
     source_environment = os.environ if environ is None else environ
+
+    # C4 version-coupling gate (#869 Point-1): before this ENFORCEMENT half
+    # chains into anything, assert that the ACTIVATION contract it is about
+    # to rely on (MOSAIC_LEASE_* injection, broker chaining) matches what
+    # this enforcement build expects. This is a build/deploy-defect check,
+    # not a broker-availability question, so it runs before — and
+    # independently of — broker registration below, and it FAILS LOUD: a
+    # clear stderr message plus a dedicated non-zero exit code, never a
+    # silent pass and never folded into the generic registration-failure
+    # branch.
+    try:
+        assert_activation_capability_matches(
+            probe_activation_capability(source_environment),
+            expected_activation_capability,
+        )
+    except VersionCouplingError as version_error:
+        print(str(version_error), file=sys.stderr)
+        return EXIT_VERSION_SKEW
+
     try:
         socket_path = Path(source_environment["MOSAIC_LEASE_BROKER_SOCKET"])
         generation = int(source_environment.get("MOSAIC_RUNTIME_GENERATION", "1"))