feat: content-addressed XXH64 op digests for TCode run caching

[SkyeAv]

Layer 1 of 7 in the TCode run-cache stack (stack #162, merges bottom-up): gives every TCode instruction run a XXH64 content address so a later layer can recognize identical instruction prefixes across sections. No behavior change in this layer.

Content addressing

• Adds src/tablassert/runcache.py with pure canonical(), op_repr(), LABEL_FREE, and prefix_digest(): identical op lists digest identically, any semantic argument change changes the digest, and unsupported argument types raise coded RunCacheError (runcache-unserializable-arg) instead of silently mis-hashing.
• Label masking: LABEL_FREE excludes the log-context-only section_hash/config_file slots of resolve_batch (stored-args positions 3/4) and fullmap_audit (1/2) so sections differing only in log labels share a digest. Positions index the stored args tuple — compile_subgraph pipes each op's leading LazyFrame through reduce, so signature index minus one.
• Hash choice: tablassert.rs.xxh64 (bundled Rust xxhash-rust, seed 0, full 16-hex digest) — the same primitive as utils.mkhash section-store keys, so no second hashing implementation or dependency.

Design

• canonical() branch ordering matters for subclasses: bool before int, Enum before str (repo enums are str, Enum).
• RunCacheError mirrors the _Coded house style (message + kebab-case code + docs URL), defined locally because TablassertErrorCodes is a closed Literal.
• Accepted caveat: callables are identified by module.qualname; lambdas would collide (mod.<lambda>). No TCode op is a lambda today.

Testing

• uv run pytest -q tests/test_run_cache.py tests/test_lib.py tests/test_utils.py → 277 passed (6 new digest tests; runcache.py 100% covered)
• uv run ruff check . → passed; uv run ruff format --check . → 90 files formatted; uv run pyright → 0 errors

[coderabbitai]

Important

• 🔍 Trigger review

This repository does not receive automatic reviews because it has fewer than 10 stars.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: 9c023894-bc52-4aff-ab2e-018dd9d3b8c3

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}