refactor(a2a): rename ACP module and symbols to A2A standard

Renamed src/cleveragents/acp/ to src/cleveragents/a2a/ and all 13
Acp* classes to A2a* per ADR-047 (A2A Standard Adoption). Updated
all imports, structlog event names (acp.* → a2a.*), field names
(acp_version → a2a_version), and test references across the entire
codebase. This is a cosmetic rename only — no behavioral changes.

ISSUES CLOSED: #688

benchmarks/a2a_facade_bench.py

@@ -0,0 +1,124 @@
+"""ASV benchmarks for A2A facade dispatch, version negotiation, and event queue.
+
+Measures the performance of:
+- A2aLocalFacade dispatch overhead per operation
+- A2aVersionNegotiator negotiation throughput
+- A2aEventQueue publish and get_events throughput
+"""
+
+from __future__ import annotations
+
+import importlib
+import sys
+from pathlib import Path
+
+# Ensure the local *source* tree is importable even when ASV has an
+# older build of the package installed.
+_SRC = str(Path(__file__).resolve().parents[1] / "src")
+if _SRC not in sys.path:
+    sys.path.insert(0, _SRC)
+
+# Force-reload so ASV picks up the source tree version.
+import cleveragents  # noqa: E402
+
+importlib.reload(cleveragents)
+
+from cleveragents.a2a.events import A2aEventQueue  # noqa: E402
+from cleveragents.a2a.facade import A2aLocalFacade  # noqa: E402
+from cleveragents.a2a.models import A2aEvent, A2aRequest  # noqa: E402
+from cleveragents.a2a.versioning import A2aVersionNegotiator  # noqa: E402
+
+# ---------------------------------------------------------------------------
+# Facade dispatch benchmarks
+# ---------------------------------------------------------------------------
+
+
+class FacadeDispatchSuite:
+    """Benchmark A2aLocalFacade.dispatch() overhead."""
+
+    timeout = 60
+
+    def setup(self) -> None:
+        self.facade = A2aLocalFacade()
+        self.session_req = A2aRequest(operation="session.create")
+        self.plan_req = A2aRequest(
+            operation="plan.execute", params={"plan_id": "BENCH001"}
+        )
+        self.context_req = A2aRequest(operation="context.get")
+
+    def time_dispatch_session_create(self) -> None:
+        self.facade.dispatch(self.session_req)
+
+    def time_dispatch_plan_execute(self) -> None:
+        self.facade.dispatch(self.plan_req)
+
+    def time_dispatch_context_get(self) -> None:
+        self.facade.dispatch(self.context_req)
+
+    def time_dispatch_all_operations(self) -> None:
+        for op in self.facade.list_operations():
+            req = A2aRequest(operation=op)
+            self.facade.dispatch(req)
+
+    def time_list_operations(self) -> None:
+        self.facade.list_operations()
+
+
+# ---------------------------------------------------------------------------
+# Version negotiation benchmarks
+# ---------------------------------------------------------------------------
+
+
+class VersionNegotiationSuite:
+    """Benchmark A2aVersionNegotiator throughput."""
+
+    timeout = 60
+
+    def setup(self) -> None:
+        self.negotiator = A2aVersionNegotiator()
+
+    def time_negotiate_supported(self) -> None:
+        self.negotiator.negotiate("1.0")
+
+    def time_is_supported_true(self) -> None:
+        self.negotiator.is_supported("1.0")
+
+    def time_is_supported_false(self) -> None:
+        self.negotiator.is_supported("99.0")
+
+    def time_get_current(self) -> None:
+        self.negotiator.get_current()
+
+
+# ---------------------------------------------------------------------------
+# Event queue benchmarks
+# ---------------------------------------------------------------------------
+
+
+class EventQueueSuite:
+    """Benchmark A2aEventQueue throughput."""
+
+    timeout = 60
+
+    def setup(self) -> None:
+        self.queue = A2aEventQueue()
+        self.event = A2aEvent(event_type="bench.event")
+
+    def time_publish_single(self) -> None:
+        self.queue.publish(self.event)
+
+    def time_publish_100(self) -> None:
+        for _ in range(100):
+            self.queue.publish(self.event)
+
+    def time_get_events_default(self) -> None:
+        self.queue.get_events()
+
+    def time_subscribe_local(self) -> None:
+        self.queue.subscribe_local(lambda e: None)
+
+    def time_publish_with_subscriber(self) -> None:
+        q = A2aEventQueue()
+        q.subscribe_local(lambda e: None)
+        for _ in range(100):
+            q.publish(self.event)