fix(ci): ignore local artifacts in license checks

[johntmyers]

Summary

Make the license-header check use Git tracked/unignored file discovery so ignored local agent artifacts under architecture/plans/ do not fail CI or pre-commit. Also fixes the malformed .claude/settings.local.json ignore entry and stabilizes the Podman Unix-socket test stub that blocked full pre-commit verification.

Related Issue

None.

Changes

• Discover license-header candidates from git ls-files --cached --others --exclude-standard by default.
• Skip explicitly provided paths when Git ignore rules exclude them.
• Fix the .claude/settings.local.json ignore rule.
• Allow Podman test stubs to tolerate Hyper shutdown after one-shot client responses.
• Normalize the stale Cargo.lock rand dependency edge updated by Cargo during verification.

Testing

• mise run pre-commit passes
• mise exec -- cargo test -p openshell-driver-podman --lib passes
• uv run ruff check scripts/update_license_headers.py passes
• uv run ruff format --check scripts/update_license_headers.py passes
• mise run license:check passes
• Explicit ignored plan-file check returns Checking 0 files for SPDX headers...

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (not applicable)

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