Three follow-ups to the previous perf commit:
1. Drop the rows_hash field on CacheEntry. The field was computed and
stored but never read on the hot path; tests exercised it only to
assert the cache returned a stable hash. After this change
get_or_compute_rows returns just Vec<OutputRow>, halving the
tuple-return ABI and removing one DefaultHasher::write pass on
every cache miss.
2. Replace DefaultHasher (SipHash) with a hand-rolled FNV-1a 64-bit
hash. SipHash is per-process-keyed and ~5-10x slower than FNV on
the small-to-medium tool output strings we see at 120 FPS. FNV-1a
has no per-process key, fits in 20 lines of pure-Rust, and a 64-bit
collision space is more than wide enough for the per-process LRU's
expected <= a few hundred entries. The cache is a correctness
optimization, not a security boundary; collisions only cause a
false miss, never wrong data.
3. Caller in tui::history::render_preserved_output_mode updated to
the new Vec<OutputRow>-only signature. Two new tests cover the
FNV-1a properties (length-suffix sensitivity, empty-input
stability).
HUQIANTAO
863f55cc68