docs(a2a): align skills Python version with package metadata

[FanouZeng-TT]

Description

a2a/SKILLS.md currently describes the backend runtime as Python 3.13:

| Backend | Python 3.13, Uvicorn, Starlette, Pydantic |

The business agent package metadata defines the supported range as Python 3.10
or newer in both source-of-truth files:

# a2a/business_agent/pyproject.toml and uv.lock
requires-python = ">=3.10"

The CLI also starts successfully under Python 3.10 (uv run --python 3.10 business_agent --help, exit 0). Calling out only 3.13 makes the context file
look more restrictive than the package it documents.

Fix: describe the backend as Python 3.10+, matching the package metadata
without changing dependencies or runtime behavior.

Category (Required)

• Core Protocol: Changes to the base communication layer, global context, or breaking refactors. (Requires Technical Council approval)
• Governance/Contributing: Updates to GOVERNANCE.md, CONTRIBUTING.md, or CODEOWNERS. (Requires Governance Council approval)
• Capability: New schemas (Discovery, Cart, etc.) or extensions. (Requires Maintainer approval)
• Documentation: Updates to README, or documentations regarding schema or capabilities. (Requires Maintainer approval)
• Infrastructure: CI/CD, Linters, or build scripts. (Requires DevOps Maintainer approval)
• Maintenance: Version bumps, lockfile updates, or minor bug fixes. (Requires DevOps Maintainer approval)
• SDK: Language-specific SDK updates and releases. (Requires DevOps Maintainer approval)
• Samples / Conformance: Maintaining samples and the conformance suite. (Requires Maintainer approval)
• UCP Schema: Changes to the ucp-schema tool (resolver, linter, validator). (Requires Maintainer approval)
• Community Health (.github): Updates to templates, workflows, or org-level configs. (Requires DevOps Maintainer approval)

Related Issues

N/A

Checklist

• I have followed the Contributing Guide (including Conventional Commits title requirements and ! for breaking changes).
• I have updated the documentation (if applicable).
• My changes pass all local linting and formatting checks.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• (For Core/Capability) I have included/updated the relevant JSON schemas.
• I have regenerated Python Pydantic models by running generate_models.sh under python_sdk.

Screenshots / Logs (if applicable)

N/A — documentation-only metadata alignment.

🤖 Generated with Claude Code

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