test(ci): locate Git Bash from MinGW Git path

[phernandez]

Summary

• locate the Git Bash launcher when shutil.which("git") resolves Git for Windows through mingw64/bin
• keep support for the top-level bin and cmd Git executable layouts
• add a platform-independent regression for the exact path shape reported by the failed Windows job

Problem

PR #1206 fixed the original direct-.sh execution failure and the WSL bash collision, but its final Windows SQLite unit job exposed one more Git-for-Windows layout. The test process resolved git.exe as C:\Program Files\Git\mingw64\bin\git.exe, while the Bash launcher lives at C:\Program Files\Git\bin\bash.exe. The locator checked only the directory containing git.exe, so all 12 shell-helper cases failed before invoking the script.

This is a test-harness correction only. The merged issue-label reconciliation and per-issue workflow serialization are unchanged.

Changes

• derive candidate Bash paths for Git executables found under bin, cmd, or mingw64/bin
• select the first existing launcher and retain a clear fail-fast error when Git Bash is unavailable
• assert that a Git/mingw64/bin/git.exe executable maps back to Git/bin/bash.exe

Testing

• uv run pytest -p pytest_mock --no-cov -q tests/test_claude_issue_triage.py — 14 passed
• bash -n scripts/edit-issue-labels.sh — passed
• git diff --check — passed
• just fast-check — passed

Evidence

• Follow-up to fix(ci): make issue triage labeling deterministic #1206
• Failed Windows job: https://github.com/basicmachines-co/basic-memory/actions/runs/31333760441/job/93296112463