Replaces 54 predictable os.tmpdir()+Date.now() test-home paths in
tests/hooks/hooks.test.js and the pid-based transcript files in
tests/lib/llm-summary.test.js with fs.mkdtempSync. The 22
claude-tool-count-* sites are left as-is: they intentionally mirror
the path the production hook computes. Clears all 16 open code-scanning
alerts (#256-#271).