fix(local): detect docker compose v2+ when version has no 'v' prefix

[mohamedzeidan2021]

Docker Compose installed via Homebrew reports its version without a leading 'v' (e.g. "Docker Compose version 2.22.0"). The detection regex v(\d+) required a literal 'v' before the digits, so _get_compose_cmd_prefix failed to recognize a valid Compose v2+ plugin in that case.

Change the regex to version\s+v?(\d+), making the 'v' optional and anchoring to the "version" keyword so a stray number elsewhere in the output can't cause a false positive. v1 is still correctly rejected.

Applied to all three v3 copies (core local image, core modules local container, train local container) with regression tests for the no-'v'-prefix format.

Fixes #4137

Issue #, if available:

Description of changes:

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PR Review — Docker Compose version detection fix

• Read PR diff and changed files
• Verify regex correctness (v2+ accept, v1 reject, no-'v'-prefix)
• Check test coverage across the three v3 copies

Verdict: ✅ Looks good

The fix is correct, minimal, and consistently applied. Changing v(\d+) → version\s+v?(\d+) in all three _get_compose_cmd_prefix copies resolves the real bug in #4137:

• Old regex v(\d+) never matched "Docker Compose version 2.22.0" — there's no v immediately followed by a digit (the v in "version" is followed by e), so brew-installed Compose was wrongly rejected. ✔️ diagnosis is accurate.
• New regex anchors on the literal version keyword and makes the v optional, so it correctly captures the major version in both "version v2.20.0" (→ 2) and "version 2.22.0" (→ 2).
• v1 is still rejected: "docker-compose version 1.29.2" → captures 1, and int("1") >= 2 is False, so it falls through to the docker-compose CLI path. Confirmed by the existing v1 tests in sagemaker-train/tests/unit/train/local/test_local_container.py (..._v1_falls_through, ..._v1_no_standalone_raises).
• Anchoring on version\s+ also tightens things vs. the old loose match, guarding against a stray v<digit> elsewhere in the output.

Tests

Regression tests for the no-'v'-prefix format were added to all three test suites (test_image.py, modules test_local_container.py, train test_local_container.py), each asserting ["docker", "compose"]. Good coverage matching the source change.

Minor (optional, non-blocking)

• The core copies (sagemaker-core/.../local/image.py and .../modules/local_core/local_container.py) don't have an explicit v1-rejection test with the new "...version 1.x" format the way the train copy does. Not introduced by this PR — the train suite already covers the v1 semantics — but adding parallel v1 tests to the core suites would fully lock in the "≥ 2" branch there too. Not required to merge.

Nothing else stood out — no correctness, security, or backward-compat concerns. The change is a pure bug fix to an internal detection helper (_get_compose_cmd_prefix, private API), so no public interface impact.
· fix/docker-compose-version-no-v-prefix-4137