fix: update a2a-sdk compatibility

[jsonmp-k8]

Summary

• update Python packages to depend on a2a-sdk >=1.0.2 and refresh uv.lock to 1.0.3
• move KAgent's internal A2A model usage to the SDK v0.3 compatibility namespace
• add compatibility shims for removed a2a-sdk 0.3 server app helpers and google-adk imports while wiring 1.x request handlers/cards
• update remote A2A tool middleware handling for the a2a-sdk 1.x client interceptor API

Testing

• /private/tmp/a2a-inspect/bin/uv run ruff format && /private/tmp/a2a-inspect/bin/uv run ruff check
• /private/tmp/a2a-inspect/bin/uv run pytest packages/kagent-core/tests/test_hitl_utils.py packages/kagent-core/tests/test_read_metadata_value.py packages/kagent-adk/tests/unittests/test_remote_a2a_tool.py packages/kagent-adk/tests/unittests/converters/test_event_converter.py packages/kagent-langgraph/tests/test_checkpointer.py (91 passed)
• /private/tmp/a2a-inspect/bin/uv run pytest ./packages/**/tests/ (458 passed, 1 skipped)

Signed-off-by: jaison paul paul.jaison@gmail.com

[jsonmp-k8]

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[Copilot]

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[jsonmp-k8]

Addressed the review concerns in the latest push:

• Verified against a2a-sdk 1.0.3 that ClientCallInterceptor only defines before/after, then removed the legacy intercept method and updated the header propagation tests to exercise before.
• Added comments around the google-adk import-order compatibility shims so the ruff E402 exceptions and restore call are intentional.
• Added a descriptive getattr to the synthetic a2a.client.middleware module for unsupported symbols.
• Capped a2a-sdk constraints at <2.0 and refreshed uv.lock.
• Documented A2AFastAPIApplication as a name-compatible alias and restored the unrelated test_sap_ai_core.py blank line.

Validation after these changes:

• /private/tmp/a2a-inspect/bin/uv run ruff format && /private/tmp/a2a-inspect/bin/uv run ruff check
• /private/tmp/a2a-inspect/bin/uv run pytest packages/kagent-core/tests/test_hitl_utils.py packages/kagent-core/tests/test_read_metadata_value.py packages/kagent-adk/tests/unittests/test_remote_a2a_tool.py packages/kagent-adk/tests/unittests/converters/test_event_converter.py packages/kagent-langgraph/tests/test_checkpointer.py (91 passed)
• /private/tmp/a2a-inspect/bin/uv run pytest ./packages/**/tests/ (458 passed, 1 skipped)

[EItanya]

Looks like the agents are failing to come up in the e2e tests