Cache content digest misses models reached through Any-typed fields

Context

#320 was caused by cache invalidation observing only properties of the source file (mtime, size, subagents fingerprint) and nothing about the shape of what we had written into messages.content. A new model field therefore stayed absent from every blob whose transcript had not changed.

The fix (#322) added a content_version digest derived from the entry models' declared field names, with mismatch or NULL treated as stale.

The residual gap

_content_models() (claude_code_log/cache.py:416) discovers models by walking the entry union through type annotations, unwrapping Optional/union/List/Dict and collecting every reachable BaseModel.

Anything that reaches a content blob without being declared as a typed field is therefore outside the digest:

• a field annotated Any that carries a model at runtime;
• a model constructed dynamically;
• any payload reaching model_dump() from outside the entry tree.

For those, adding a field does not move the digest, and #320's exact failure mode is still live.

Why this is not hypothetical

UserTranscriptEntry.imagePasteIds is itself Optional[Any] (claude_code_log/models.py:273) — the very field whose absence caused #320. So the codebase does use Any where a real shape exists.

Notes

• This was left open deliberately rather than closed under time pressure; it was named as the sharpest remaining question when the digest work was reviewed.
• _CONTENT_SCHEMA_SALT (cache.py:399) is the manual escape hatch meanwhile: bumping it invalidates every cache.
• Hashing types or annotations rather than names was considered and rejected — it would mass-invalidate on a Pydantic or Python upgrade.

Possible directions

Enumerate BaseModel subclasses in the package rather than walking annotations from a root; or narrow the Any-typed fields that actually carry models to real types; or assert in a test that every BaseModel in the package is reachable from the walk, so a new unreachable one fails loudly.

Start with _content_models() in claude_code_log/cache.py and the Optional[Any] imagePasteIds field in claude_code_log/models.py. Compare the proposed discovery strategies and inspect the existing content_version behavior from #322. Done means an unreachable or runtime-carried model can no longer leave the cache digest unchanged, with a test or explicit coverage assertion for the chosen approach.