feat(a4,c3b): complete A-4 Phase 2 agent knowledge migration & Option B isolation removal

- Option B / C-3b: Deprecate isolation.root and remove its 4 legacy consumers in lib.sh, workspace_uuid.py, verify_session.py, and stop_session.sh.
- M2~M7 Migration: Implement artifact_path, verify_artifact, purge_artifacts, spawn_spec, resume_spec, auth_ok, discover, ready_tokens, exit_key, and delegate_agent_key across BaseAgentAdapter and all 4 adapters (Claude, Agy, Hermes, Cline).
- Migrate shell duplications in lib.sh, create_session.sh, resume_session.sh, stop_session.sh, and reconcile.sh to python -m lib_py.agents facts.
- Hardening & Corrections: Fix Cline resume_spec flag to '-i --id', apply shlex.quote across all facts variables with MAM_ prefix, add safe fallback in wait_for_tui_ready.
- Add comprehensive contract tests in tests/test_a4_adapter_contract.py and sync IMPROVEMENTS.md / LOG.md.
- Verified: 100% PASS across unit, component, contract, and integration tests.

.agents/skills/lib_py/agents/adapters/agy.py

@@ -1,6 +1,6 @@
-# agy.py — Antigravity (agy) agent adapter
-
-from lib_py.agents.base import BaseAgentAdapter
+import os, json, sqlite3, shutil
+from typing import Optional, Any
+from lib_py.agents.base import BaseAgentAdapter, DiscoveryContext
 
 class AgyAgentAdapter(BaseAgentAdapter):
     @property
@@ -11,6 +11,22 @@ class AgyAgentAdapter(BaseAgentAdapter):
     def own_key(self) -> str:
         return 'agy_conversation_id_own'
 
+    @property
+    def ready_tokens(self) -> str:
+        return 'Antigravity'
+
+    @property
+    def exit_key(self) -> str:
+        return 'Exit'
+
+    @property
+    def delegate_agent_key(self) -> str:
+        return 'antigravity-cli'
+
+    @property
+    def identity_cache_fields(self) -> tuple:
+        return ('conversation_id', 'conversation_db', 'conversation_brain_dir')
+
     @property
     def input_prompt(self) -> str:
         return '>'
@@ -22,3 +38,71 @@ class AgyAgentAdapter(BaseAgentAdapter):
     @property
     def input_rule_pattern(self) -> str:
         return '─{10,}'
+
+    def artifact_path(self, uuid: str, ctx: DiscoveryContext) -> str:
+        return f"{ctx.home_dir}/.gemini/antigravity-cli/conversations/{uuid}.db"
+
+    def verify_artifact(self, uuid: str, ctx: DiscoveryContext) -> bool:
+        path = self.artifact_path(uuid, ctx)
+        if not os.path.exists(path):
+            return False
+        if ctx.epoch and os.path.getmtime(path) < ctx.epoch:
+            return False
+        if ctx.mode == "discover":
+            lc = f"{ctx.home_dir}/.gemini/antigravity-cli/cache/last_conversations.json"
+            cache_match = False
+            if os.path.exists(lc):
+                try:
+                    with open(lc) as f:
+                        lc_data = json.load(f)
+                    cache_match = (lc_data.get(ctx.cwd) == uuid)
+                except Exception:
+                    cache_match = False
+            if not cache_match:
+                if uuid in (ctx.row.get("_sibling_claimed_uuids") or []):
+                    return False
+        try:
+            conn = sqlite3.connect(path)
+            r = conn.execute("SELECT count(*) FROM steps").fetchone()
+            conn.close()
+            if not r or r[0] < 1:
+                return False
+        except Exception:
+            return False
+        return True
+
+    def purge_artifacts(self, uuid: str, ctx: DiscoveryContext) -> list:
+        purged = []
+        db = self.artifact_path(uuid, ctx)
+        if os.path.exists(db):
+            os.remove(db)
+            purged.append(db)
+        brain = f"{ctx.home_dir}/.gemini/antigravity-cli/brain/{uuid}"
+        if os.path.isdir(brain):
+            shutil.rmtree(brain, ignore_errors=True)
+            purged.append(brain)
+        return purged
+
+    def spawn_spec(self, binary: str, session_uuid: str = "", use_wrapper: bool = False) -> str:
+        return f"{binary} --dangerously-skip-permissions"
+
+    def resume_spec(self, binary: str, session_uuid: str, materialized: bool = False) -> str:
+        if materialized and session_uuid:
+            return f"{binary} --dangerously-skip-permissions --conversation {session_uuid}"
+        return f"{binary} --dangerously-skip-permissions"
+
+    def auth_ok(self, run_cmd: Optional[Any] = None) -> bool:
+        home = os.environ.get("HOME_DIR") or os.environ.get("HOME") or os.path.expanduser("~")
+        return os.path.exists(f"{home}/.gemini/oauth_creds.json") or os.path.exists(f"{home}/.gemini/antigravity-cli/antigravity-oauth-token")
+
+    def discover(self, ctx: DiscoveryContext) -> list:
+        lc = f"{ctx.home_dir}/.gemini/antigravity-cli/cache/last_conversations.json"
+        if os.path.exists(lc):
+            try:
+                with open(lc) as f:
+                    cand = json.load(f).get(ctx.workspace)
+                if cand and self.verify_artifact(cand, ctx):
+                    return [cand]
+            except Exception:
+                pass
+        return []