fix(bma): set requires-python >=3.12 so uv run client.py does not use an older system Python

[siwachabhi]

Description

The BedrockManagedAgents template has no requires-python in pyproject.toml. On macOS, uv run client.py can then pick the system Python 3.9, and openai does not install on it.

This PR sets requires-python = ">=3.12" in the template pyproject.toml. It is a minimum only. The Dockerfile still runs uv python install --default before it copies pyproject.toml, so the image keeps the latest Python, and uv sync checks the minimum.

Changes:

• src/assets/python/http/bma/base/pyproject.toml: add requires-python = ">=3.12".
• src/assets/python/http/bma/base/README.md: tell the reader why the minimum is there.
• src/cli/templates/__tests__/bma.test.ts: check the minimum, and check that the image installs Python before it copies pyproject.toml.
• Updated asset snapshots (2 lines).

Related Issue

No issue. The problem came from feedback on the BMA getting started guide.

Documentation PR

None.

Type of Change

• Bug fix

Testing

• npx vitest run --project unit src/cli/templates/__tests__/bma.test.ts src/assets/__tests__/assets.snapshot.test.ts (164 passed)
• npm run typecheck
• eslint and prettier on the changed files (pre-commit hook)
• Updated the asset snapshots
• Full npm run test:unit and npm run test:integ not run

Checklist

• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• My changes generate no new warnings

[agentcore-devx-automation]

Claude Security Review: no high-confidence findings. (run)

[agentcore-devx-automation]

AgentCore Harness Review

Verdict: Looks good

Small, focused change that adds requires-python = ">=3.12" to the BMA pyproject.toml template so uv run client.py doesn't fall back to a system Python 3.9 (which the openai SDK no longer supports). Consistent with the other Python templates, which all set a requires-python minimum.

A few observations, none blocking:

• The >=3.12 bound is stricter than strictly needed for the stated reason (openai SDK dropped 3.9, so >=3.10 would suffice, and matches most other templates). If there's a specific reason for 3.12 over 3.10 it might be worth noting in the README paragraph; otherwise >=3.10 would be more permissive for client environments. Not a blocker either way.
• The updated test nicely asserts that RUN uv python install --default runs before COPY pyproject.toml so the minimum doesn't inadvertently pin the image build. Good defensive check.
• Uses real fs reads against generated output — no excessive mocking. No telemetry needed for a template constant change.

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	41.28%	15848 / 38384
🔵	Statements	40.55%	16912 / 41697
🔵	Functions	35.37%	2730 / 7718
🔵	Branches	34.47%	10621 / 30805

Generated in workflow #4500 for commit 5efb467 by the Vitest Coverage Report Action