fix(ci): correct ruff lint errors and Python 3.10 syntax in security patch

- Remove module-level research docstrings from card_resolver.py and
    default_request_handler.py (originals have none; D415 lint failure)
- Add missing docstrings to five push-notification handler methods
    that existed in the original SDK (D102 lint failure)
- Fix import ordering in card_resolver.py and url_validation.py (I001)
- Convert double-quoted string literals to single quotes throughout
    both patched source files (Q000; project uses quote-style = single)
- Restore parentheses in except clause:
    except (asyncio.CancelledError, GeneratorExit):
    Bare tuple syntax was added in Python 3.14; CI targets Python 3.10
    where it raises SyntaxError (ruff had silently removed the parens)

Author: amit-raut

src/a2a/client/card_resolver.py

@@ -1,16 +1,3 @@
-"""Patched version of a2a/client/card_resolver.py
-
-Fix for A2A-SSRF-01: validate AgentCard.url before returning the card.
-
-Diff summary vs. original (v0.3.25):
-  + import A2ASSRFValidationError, validate_agent_card_url from a2a.utils.url_validation
-  + call validate_agent_card_url(agent_card.url) after model_validate()
-  + wrap in try/except to raise A2AClientJSONError with a clear SSRF message
-  + validate additional_interfaces[*].url as well (same attack surface)
-
-Target file: src/a2a/client/card_resolver.py
-"""
-
 import json
 import logging
 
@@ -19,8 +6,6 @@
 
 import httpx
 
-from pydantic import ValidationError
-
 from a2a.client.errors import (
     A2AClientHTTPError,
     A2AClientJSONError,
@@ -29,11 +14,11 @@
     AgentCard,
 )
 from a2a.utils.constants import AGENT_CARD_WELL_KNOWN_PATH
-
-# ---- NEW IMPORT (fix for A2A-SSRF-01) ----
-from a2a.utils.url_validation import A2ASSRFValidationError, validate_agent_card_url
-
-# -------------------------------------------
+from a2a.utils.url_validation import (
+    A2ASSRFValidationError,
+    validate_agent_card_url,
+)
+from pydantic import ValidationError
 
 
 logger = logging.getLogger(__name__)
@@ -55,8 +40,8 @@ def __init__(
             base_url: The base URL of the agent's host.
             agent_card_path: The path to the agent card endpoint, relative to the base URL.
         """
-        self.base_url = base_url.rstrip("/")
-        self.agent_card_path = agent_card_path.lstrip("/")
+        self.base_url = base_url.rstrip('/')
+        self.agent_card_path = agent_card_path.lstrip('/')
         self.httpx_client = httpx_client
 
     async def get_agent_card(
@@ -89,9 +74,9 @@ async def get_agent_card(
         if not relative_card_path:
             path_segment = self.agent_card_path
         else:
-            path_segment = relative_card_path.lstrip("/")
+            path_segment = relative_card_path.lstrip('/')
 
-        target_url = f"{self.base_url}/{path_segment}"
+        target_url = f'{self.base_url}/{path_segment}'
 
         try:
             response = await self.httpx_client.get(
@@ -101,13 +86,13 @@ async def get_agent_card(
             response.raise_for_status()
             agent_card_data = response.json()
             logger.info(
-                "Successfully fetched agent card data from %s: %s",
+                'Successfully fetched agent card data from %s: %s',
                 target_url,
                 agent_card_data,
             )
             agent_card = AgentCard.model_validate(agent_card_data)
 
-            # ---- FIX: A2A-SSRF-01 -- validate card.url before returning ----
+            # Validate card.url before returning (fix for A2A-SSRF-01).
             # Without this check, any caller who controls the card endpoint
             # can redirect all subsequent RPC calls to an internal address.
             try:
@@ -117,30 +102,29 @@ async def get_agent_card(
                     validate_agent_card_url(iface.url)
             except A2ASSRFValidationError as e:
                 raise A2AClientJSONError(
-                    f"AgentCard from {target_url} failed SSRF URL validation: {e}"
+                    f'AgentCard from {target_url} failed SSRF URL validation: {e}'
                 ) from e
-            # -----------------------------------------------------------------
 
             if signature_verifier:
                 signature_verifier(agent_card)
 
         except httpx.HTTPStatusError as e:
             raise A2AClientHTTPError(
                 e.response.status_code,
-                f"Failed to fetch agent card from {target_url}: {e}",
+                f'Failed to fetch agent card from {target_url}: {e}',
             ) from e
         except json.JSONDecodeError as e:
             raise A2AClientJSONError(
-                f"Failed to parse JSON for agent card from {target_url}: {e}"
+                f'Failed to parse JSON for agent card from {target_url}: {e}'
             ) from e
         except httpx.RequestError as e:
             raise A2AClientHTTPError(
                 503,
-                f"Network communication error fetching agent card from {target_url}: {e}",
+                f'Network communication error fetching agent card from {target_url}: {e}',
             ) from e
         except ValidationError as e:
             raise A2AClientJSONError(
-                f"Failed to validate agent card structure from {target_url}: {e.json()}"
+                f'Failed to validate agent card structure from {target_url}: {e.json()}'
             ) from e
 
         return agent_card