Tests

Lazy-load chat histories, fast list summaries, and mtime disk cache (closes #84) #163

Job	Run time
Secret scan (gitleaks)	4s
Unit tests (windows-latest / Python 3.10)	1m 16s
Unit tests (ubuntu-latest / Python 3.10)	24s
Unit tests (windows-latest / Python 3.12)	1m 25s
Unit tests (ubuntu-latest / Python 3.13)	21s
Unit tests (ubuntu-latest / Python 3.12)	23s
Unit tests (windows-latest / Python 3.11)	59s
Unit tests (macos-latest / Python 3.10)	36s
Lock file freshness	11s
Unit tests (ubuntu-latest / Python 3.11)	20s
Unit tests (macos-latest / Python 3.12)	20s
Unit tests (macos-latest / Python 3.11)	16s
Typecheck (mypy)	17s
Unit tests (windows-latest / Python 3.13)	59s
Unit tests (macos-latest / Python 3.13)	16s
	8m 7s

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