```

fix(a2a): update A2aVersionNegotiator to support JSON-RPC version 2.0

Implemented changes to align the A2A version negotiation with JSON-RPC 2.0 as per the specification and updated the test suite accordingly.

What was implemented
- Updated A2aVersionNegotiator.CURRENT_VERSION from "1.0" to "2.0" in src/cleveragents/a2a/versioning.py
- Updated A2aVersionNegotiator.SUPPORTED_VERSIONS from ("1.0",) to ("2.0",) in src/cleveragents/a2a/versioning.py
- Updated 7 Behave scenarios in features/consolidated_misc.feature to reflect "2.0" as the supported version:
  - Negotiate supported version succeeds: now negotiates "2.0" instead of "1.0"
  - Negotiate unsupported version raises error: now uses "99.0" as the unsupported version (since "2.0" is now supported)
  - is_supported returns True for valid version: now checks "2.0" instead of "1.0"
  - get_current returns current version: now expects "2.0" instead of "1.0"
  - M6 smoke A2A version negotiation accepts 2.0: updated from "1.0" to "2.0"
  - M6 smoke A2A version negotiation rejects unsupported: now uses "99.0" instead of "2.0"
  - M6 smoke A2A version is_supported returns correct result: now checks "2.0" instead of "1.0"

Key design decisions
- The A2A protocol is built on JSON-RPC 2.0 per the specification. The version negotiator must be consistent with JSONRPC_VERSION = "2.0" in models.py.
- "1.0" is removed from SUPPORTED_VERSIONS as there is no backward compatibility requirement for the old version in the spec.
- All tests updated to reflect the corrected behavior.

Impacted modules/components
- src/cleveragents/a2a/versioning.py
- features/consolidated_misc.feature
- Behavioral tests referencing A2A version negotiation

ISSUES CLOSED: #2747
```

COMMIT_MSG.txt

@@ -0,0 +1,29 @@
+```
+fix(a2a): update A2aVersionNegotiator to support JSON-RPC version 2.0
+
+Implemented changes to align the A2A version negotiation with JSON-RPC 2.0 as per the specification and updated the test suite accordingly.
+
+What was implemented
+- Updated A2aVersionNegotiator.CURRENT_VERSION from "1.0" to "2.0" in src/cleveragents/a2a/versioning.py
+- Updated A2aVersionNegotiator.SUPPORTED_VERSIONS from ("1.0",) to ("2.0",) in src/cleveragents/a2a/versioning.py
+- Updated 7 Behave scenarios in features/consolidated_misc.feature to reflect "2.0" as the supported version:
+  - Negotiate supported version succeeds: now negotiates "2.0" instead of "1.0"
+  - Negotiate unsupported version raises error: now uses "99.0" as the unsupported version (since "2.0" is now supported)
+  - is_supported returns True for valid version: now checks "2.0" instead of "1.0"
+  - get_current returns current version: now expects "2.0" instead of "1.0"
+  - M6 smoke A2A version negotiation accepts 2.0: updated from "1.0" to "2.0"
+  - M6 smoke A2A version negotiation rejects unsupported: now uses "99.0" instead of "2.0"
+  - M6 smoke A2A version is_supported returns correct result: now checks "2.0" instead of "1.0"
+
+Key design decisions
+- The A2A protocol is built on JSON-RPC 2.0 per the specification. The version negotiator must be consistent with JSONRPC_VERSION = "2.0" in models.py.
+- "1.0" is removed from SUPPORTED_VERSIONS as there is no backward compatibility requirement for the old version in the spec.
+- All tests updated to reflect the corrected behavior.
+
+Impacted modules/components
+- src/cleveragents/a2a/versioning.py
+- features/consolidated_misc.feature
+- Behavioral tests referencing A2A version negotiation
+
+ISSUES CLOSED: #2747
+```

features/consolidated_misc.feature

@@ -223,20 +223,20 @@ Feature: Consolidated Misc
 
   Scenario: Negotiate supported version succeeds
     Given a new A2aVersionNegotiator
-    When I negotiate version "1.0"
-    Then the negotiated version should be "1.0"
+    When I negotiate version "2.0"
+    Then the negotiated version should be "2.0"
 
 
   Scenario: Negotiate unsupported version raises error
     Given a new A2aVersionNegotiator
-    When I try to negotiate version "2.0"
+    When I try to negotiate version "99.0"
     Then an A2aVersionMismatchError should be raised
-    And the error requested_version should be "2.0"
+    And the error requested_version should be "99.0"
 
 
   Scenario: is_supported returns True for valid version
     Given a new A2aVersionNegotiator
-    Then version "1.0" should be supported
+    Then version "2.0" should be supported
 
 
   Scenario: is_supported returns False for invalid version
@@ -246,7 +246,7 @@ Feature: Consolidated Misc
 
   Scenario: get_current returns current version
     Given a new A2aVersionNegotiator
-    Then the current version should be "1.0"
+    Then the current version should be "2.0"
 
     # -----------------------------------------------------------------------
     # A2aRequest model validation
@@ -719,24 +719,24 @@ Feature: Consolidated Misc
     # --- A2A version negotiation ---
 
 
-  Scenario: M6 smoke A2A version negotiation accepts 1.0
+  Scenario: M6 smoke A2A version negotiation accepts 2.0
     Given a m6 smoke test runner
     And a m6 smoke A2A local facade
-    When I m6 smoke negotiate A2A version "1.0"
-    Then the m6 smoke negotiated version should be "1.0"
+    When I m6 smoke negotiate A2A version "2.0"
+    Then the m6 smoke negotiated version should be "2.0"
 
 
   Scenario: M6 smoke A2A version negotiation rejects unsupported
     Given a m6 smoke test runner
     And a m6 smoke A2A local facade
-    When I m6 smoke negotiate A2A version "2.0"
+    When I m6 smoke negotiate A2A version "99.0"
     Then the m6 smoke facade should raise A2aVersionMismatchError
 
 
   Scenario: M6 smoke A2A version is_supported returns correct result
     Given a m6 smoke test runner
     And a m6 smoke A2A local facade
-    When I m6 smoke check if version "1.0" is supported
+    When I m6 smoke check if version "2.0" is supported
     Then the m6 smoke version support should be true
     When I m6 smoke check if version "99.0" is supported
     Then the m6 smoke version support should be false

src/cleveragents/a2a/versioning.py

@@ -17,8 +17,8 @@ logger: structlog.stdlib.BoundLogger = structlog.get_logger(__name__)
 class A2aVersionNegotiator:
     """Negotiates A2A protocol versions."""
 
-    CURRENT_VERSION: str = "1.0"
-    SUPPORTED_VERSIONS: tuple[str, ...] = ("1.0",)
+    CURRENT_VERSION: str = "2.0"
+    SUPPORTED_VERSIONS: tuple[str, ...] = ("2.0",)
 
     def negotiate(self, requested: str) -> str:
         """Return *requested* if supported, otherwise raise.