fix(a2a): correct issue references and fix documentation compliance

Issue references corrected from #264 to #691 throughout all documentation.
The A2A stdio transport feature is tracked by issue #691, not #264 (which was
about resource registry tables in v3.0.0).

CHANGELOG.md: Updated issue reference and added .py path routing fix entry under

BDD tests: Added command construction assertions for all three connect scenarios
(module, .py script, executable) to verify subprocess.Popen receives correct args:
- Module paths (cleveragents.X): [python, -m, module]
- .py file paths: [python, file.py]
- Executable paths: [executable_path]

CONTRIBUTORS.md

@@ -97,7 +97,7 @@ Below are some of the specific details of various contributions.
 * HAL 9000 <hal9000@cleverthis.com> has contributed cost and session budget tracking and enforcement (issue #8609): implemented `CostTrackingService`, `BudgetExceededError`, three-tier budget hierarchy (plan/session/organization), warning thresholds at 90% utilization, per-provider cost tracking, and comprehensive BDD test suite.
 * HAL 9000 has contributed the AutoDebug node state mutation fix (#10496): fixed _analyze_error, _generate_fix, and _validate_fix in src/cleveragents/agents/graphs/auto_debug.py to return partial update dicts per LangGraph s node contract, preventing duplicate state entries and checkpoint inconsistencies.
 * HAL 9000 has contributed the ContextStrategy protocol and plugin registration system (PR #11106 / issue #8616): implemented the domain-model `ContextStrategy` Protocol with BackendSet, PlanContext, StrategyCapabilities, StrategyConfig, ContextStrategyResult, and StrategyRegistryEntry models. Six built-in strategies each implement real backend query logic respecting budget constraints. The StrategyRegistry service provides thread-safe registration/unregistration, Pydantic-validated config updates with immutable MappingProxyType fields, plugin discovery via register_from_module() with CWE-706 module-prefix allowlist guard, enabled list management, deterministic fragment ordering, and validation warnings. Comprehensive BDD test coverage in features/context_strategies.feature and features/context_strategy_registry.feature (120+ scenarios) (#8616).
-* HAL 9000 has contributed the A2A stdio transport for local mode (#264): implemented ``A2aStdioTransport`` class with JSON-RPC 2.0 message framing over stdin/stdout for subprocess communication, including process lifecycle management (connect/disconnect), request/response serialization, graceful shutdown with timeout-based termination, and type-safe path resolution for Python modules vs. executable scripts. Added full BDD test coverage (18 scenarios) in ``features/a2a_stdio_transport.feature`` with mock subprocess behavior in step definitions.
+* HAL 9000 has contributed the A2A stdio transport for local mode (#691): implemented ``A2aStdioTransport`` class with JSON-RPC 2.0 message framing over stdin/stdout for subprocess communication, including process lifecycle management (connect/disconnect), request/response serialization, graceful shutdown with timeout-based termination, and type-safe path resolution for Python modules vs. executable scripts. Added full BDD test coverage (18 scenarios) in ``features/a2a_stdio_transport.feature`` with mock subprocess behavior in step definitions.
 
 # Details (PR Contributions)
 

features/a2a_stdio_transport.feature

@@ -96,6 +96,7 @@ Feature: A2A stdio transport for local-mode communication
     And subprocess Popen is mocked to succeed
     When I connect with agent path "cleveragents.a2a.agent"
     Then the stdio transport should be connected
+    And subprocess Popen should have been called with python -m module args
 
   @coverage
   Scenario: Connect with executable path
@@ -103,6 +104,7 @@ Feature: A2A stdio transport for local-mode communication
     And subprocess Popen is mocked to succeed
     When I connect with agent path "/usr/local/bin/agent"
     Then the stdio transport should be connected
+    And subprocess Popen should have been called with direct executable args
 
   @coverage
   Scenario: Connect with .py file path
@@ -110,6 +112,7 @@ Feature: A2A stdio transport for local-mode communication
     And subprocess Popen is mocked to succeed
     When I connect with agent path "agent.py"
     Then the stdio transport should be connected
+    And subprocess Popen should have been called with python script args
 
   @coverage
   Scenario: Connect raises for file not found

features/steps/a2a_stdio_transport_steps.py

@@ -5,6 +5,7 @@ from __future__ import annotations
 
 import json
 import subprocess
+import sys
 from typing import Any
 from unittest.mock import MagicMock, patch
 
@@ -281,3 +282,38 @@ def step_terminate_called(context: Any) -> None:
 def step_runtime_agent_not_found(context: Any) -> None:
     assert isinstance(context.raised_error, RuntimeError)
     assert "agent not found" in str(context.raised_error).lower()
+
+
+# ── Command construction assertions (reviewer point 5) ─────────────────────
+
+
+@then("subprocess Popen should have been called with python -m module args")
+def step_assert_popen_module_args(context: Any) -> None:
+    """Assert that for a module path, Popen received [python, -m, module]."""
+    context.popen_patcher.stop()
+    call_args = context.popen_mock.call_args
+    cmd_list = call_args[0][0]
+    assert len(cmd_list) >= 3
+    assert cmd_list[0] == sys.executable
+    assert cmd_list[1] == "-m"
+
+
+@then("subprocess Popen should have been called with python script args")
+def step_assert_popen_script_args(context: Any) -> None:
+    """Assert that for a .py file path, Popen received [python, file.py]."""
+    context.popen_patcher.stop()
+    call_args = context.popen_mock.call_args
+    cmd_list = call_args[0][0]
+    assert len(cmd_list) >= 2
+    assert cmd_list[0] == sys.executable
+    assert cmd_list[1].endswith(".py")
+
+
+@then("subprocess Popen should have been called with direct executable args")
+def step_assert_popen_executable_args(context: Any) -> None:
+    """Assert that for an executable path, Popen received [executable_path] only."""
+    context.popen_patcher.stop()
+    call_args = context.popen_mock.call_args
+    cmd_list = call_args[0][0]
+    assert len(cmd_list) >= 1
+    assert cmd_list[0].startswith("/")