ci: upgrade action versions, add uv cache, fix broken paths, DRY publish

[KRRT7]

Summary

• Action version bumps: checkout v4/v5→v6, setup-node v4→v6, setup-java v4→v5, prek-action v1→v2, github-script v6→v7, aws-credentials v4→v6, claude-code-action v1.0.89→v1
• uv caching: Added enable-cache: true to all astral-sh/setup-uv steps across all workflows (~30-60s savings per job)
• Remove redundant uv venv --seed: uv sync creates venvs automatically
• Merge double uv sync: Combined uv sync + conditional uv sync --group tests into a single step in unit-tests
• Fix codeflash.yaml: Path filter and working-directory referenced non-existent code_to_optimize_js_esm/ — fixed to code_to_optimize/js/code_to_optimize_js_esm/
• DRY publish.yml: Consolidated two near-identical publish jobs into a single matrix job (-30 lines)
• Remove generate_release_notes: true: Was overridden by the manual body: anyway

Files changed

File	Changes
ci.yaml	All version bumps, uv cache, merge sync steps, remove venv --seed
claude.yml	Version bumps, uv cache, remove venv --seed
codeflash-optimize.yaml	checkout v6, uv cache
codeflash.yaml	Fix broken paths, version bumps, add cache-dependency-path
label-workflow-changes.yml	github-script v6→v7
publish.yml	checkout v6, matrix DRY, uv cache, remove generate_release_notes

Test plan

• CI passes on this PR (prek + determine-changes gate job)
• Verify codeflash.yaml path filter matches actual directory structure
• Verify publish.yml matrix if: logic correctly gates per-package runs