--no-cache on a directory serves stale HTML when a source grows

[cboos]

Summary

claude-code-log <projectdir> --no-cache does not regenerate combined_transcripts.html when a session .jsonl grows between runs — it serves stale HTML.

Repro

claude-code-log <projectdir> --no-cache        # writes combined_transcripts.html
# ... a session in <projectdir> progresses (its .jsonl grows) ...
claude-code-log <projectdir> --no-cache        # prints "is current, skipping regeneration"
# combined_transcripts.html still lacks the new content

Cause

With --no-cache, cache_manager is None, so the directory falls into the
single-file/no-cache fallback branch in convert_jsonl_to. That branch's
freshness check (source_is_newer) is deliberately scoped to file sources
(input_path.is_file()), because a directory has no single mtime. With no
cache to track per-source mtimes either, should_regenerate is driven only by
the embedded tool version (is_outdated), which an unchanged-version regrow
does not trip → skip → stale output.

The normal (cached) directory path is unaffected: it tracks source mtimes in
its DB (is_html_stale) and regenerates correctly.

Scope / relationship

Pre-existing; it is the directory-source analogue of the single-file staleness
fixed in #221 / PR #253 (which is scoped to file sources). Filed so it isn't
forgotten. A fix would need a directory-wide freshness signal for the no-cache
path (e.g. max source mtime vs. output mtime).