refactor: update SDK path references to a2ui_agent subdirectory across samples, CI, and scripts

[nan-yu]

No description provided.

[gemini-code-assist]

Code Review

This pull request restructures the repository by moving the Python SDK into a subdirectory (agent_sdks/python/a2ui_agent). This change requires updating conformance test paths, formatting scripts, and dependency references in pyproject.toml and uv.lock files across various samples and evaluation tools. The feedback suggests a best practice improvement in scripts/fix_format.sh to handle potential failures of the cd command by appending || exit 1 to prevent subsequent commands from executing in the wrong directory.

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[gemini-code-assist]

It is a best practice to handle potential failures of the cd command in shell scripts. If the directory does not exist or cannot be accessed, the script will continue executing subsequent commands (such as uv run pyink) in the wrong directory, which can lead to unexpected behavior or formatting the wrong files. Appending || exit 1 ensures the script terminates immediately if the directory change fails.

Suggested change

	cd "$REPO_ROOT/agent_sdks/python/a2ui_agent"
	cd "$REPO_ROOT/agent_sdks/python/a2ui_agent" || exit 1