fix(aws-strands): lower Python floor to 3.10

[Vishal0203]

Fixes #2282

Problem

ag_ui_strands declares requires-python = ">=3.12, <3.14", which blocks environments pinned to Python 3.10. As reported in #2282, users currently have to patch the package locally to install it.

Notably the package README has advertised - Python 3.10+ under Prerequisites since the integration first landed in #675 — the same commit that set the floor to >=3.12. So the documented contract and the enforced metadata have disagreed from the start; this PR makes the metadata match the promise.

Why 3.10 is safe

Nothing in the adapter needs 3.11+:

• Syntax: every file under src/, tests/, and examples/ parses with ast.parse(..., feature_version=(3, 10)). The only modern constructs are PEP 604 unions (X | None), which are 3.10+ at runtime. No match statements, StrEnum, TaskGroup, ExceptionGroup/except*, itertools.batched, typing.Self, @override, datetime.UTC, or tomllib.
• Dependencies: all of them already support 3.10 — strands-agents is >=3.10 (classified 3.10–3.13), ag-ui-a2ui-toolkit is >=3.10,<3.15, ag-ui-protocol is >=3.9. Sibling integrations in this repo are already on 3.10 (langgraph, adk-middleware, agent-spec, langroid, crew-ai), so aws-strands was the outlier.

Changes

• pyproject.toml — requires-python = ">=3.10, <3.14"
• examples/pyproject.toml — python = "<3.14,>=3.10"
• examples/README.md — supported range now reads 3.10 – 3.13
• uv.lock — regenerated; adds 3.10 backports (exceptiongroup, tomli, backports-asyncio-runner) behind python_full_version < '3.11' markers

One incidental fix: regenerating the lock also moves ag-ui-a2ui-toolkit 0.0.3 → 0.0.4. The committed pyproject.toml already required >=0.0.4 while the lock still pinned 0.0.3, so uv lock --check was failing on main before this PR. Happy to split that out if you'd prefer it separate.

The upper bound <3.14 is unchanged — this only lowers the floor.

Verification (CPython 3.10.20)

• uv sync --python 3.10 --frozen --all-groups — resolves and installs
• import ag_ui_strands — all 20 public exports load
• pytest tests/ — 176 passed, 2 skipped
• poetry install in examples/ on a 3.10 interpreter, then import server.__main__ — OK
• uv build — built wheel reports Requires-Python: <3.14,>=3.10

No CI changes needed: no workflow pins a Python version for this package, and build-python-preview only runs uv build.

[Vishal0203]

Hi @ranst91 , sorry for the tag. Would appreciate a review. This will unblock us!

[aviau]

Is there even still a reason for <3.14 ?