Feat v0.9.6 deprecate stage_type, collapse stage_mode

stage_type no longer validated — starlark_hook presence determines
automation. stage_mode collapsed from 4→3 values (form/delegated/
automated); "review" mapped to "form" on input for backward compat.
Migration 018 converts existing rows. Review surface removed (~110
lines). 4 package manifests updated.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ci/e2e-workflow-nochat.sh

@@ -125,7 +125,7 @@ REVIEW_RESP=$(curl -sf -X POST "${SERVER_URL}/api/v1/workflows/${WF_ID}/stages"
   -H "$AUTH" -H "Content-Type: application/json" \
   -d '{
     "name": "Manager Review",
-    "stage_mode": "review",
+    "stage_mode": "form",
     "ordinal": 1
   }' 2>/dev/null || echo '{"error":"failed"}')