Add runtime validation gate and known issues baseline

docs/migration.md

@@ -47,6 +47,8 @@ delivery gradually, not through a single risky cutover.
 - decompression failures
 - manifest signature failures
 - key mismatch by `key_id`
+- runtime smoke against the real client
+- scenario gate with known-issues baseline
 
 ## Practical migration loop
 
@@ -55,8 +57,31 @@ delivery gradually, not through a single risky cutover.
 3. Verify it.
 4. Diff it against the source tree.
 5. Boot the client with runtime keys.
-6. Validate asset loads in logs and in-game.
-7. Move to the next pack group.
+6. Run the runtime scenario gate.
+7. Validate asset loads in logs and in-game.
+8. Move to the next pack group.
+
+Recommended gate command:
+
+```bash
+python3 scripts/validate_runtime_gate.py \
+  --runtime-root /tmp/m2dev-client-runtime-http
+```
+
+For release tightening:
+
+```bash
+python3 scripts/validate_runtime_gate.py \
+  --runtime-root /tmp/m2dev-client-runtime-http \
+  --strict-known-issues
+```
+
+The shared baseline lives in:
+
+- `known_issues/runtime_known_issues.json`
+
+This lets the migration fail only on new regressions while still tracking
+historical client data problems explicitly.
 
 ## Confirmed startup-safe pack group
 
@@ -170,6 +195,13 @@ effect files and reports 12 concrete missing references:
 - `effect/background/turtle_statue_tree_roof_light01.mse` missing `turtle_statue_tree_roof_light01.mde`
 - `effect/etc/compete/ready.mse` missing `ready.DDS`
 
+Those current actor and effect findings are also recorded in:
+
+- `known_issues/runtime_known_issues.json`
+
+That file is now the shared runtime baseline used by the validators and the
+aggregated release gate.
+
 Recommended next pack groups:
 
 1. remaining startup-adjacent patch packs