#13292
Page maps previously allowed a 100% load factor. Once live entries
and tombstones filled every slot, a missing-key lookup or insertion
could scan the entire map.
Reserve 20% of each offset hash map as insertion headroom and track
that budget separately from the live count. Port the allocation-free
in-place rehash from Zig HashMapUnmanaged so canonical insertion can
rebuild fragmented probes and restore tombstone-exhausted headroom
without growing the page. Assumed-capacity insertion now applies the
same guard, preventing the headroom counter from wrapping.
Pass the exact requested hyperlink count into map layout before
load-factor scaling, avoiding a redundant power-of-two rounding step.
Screen-level recovery now grows only when live hyperlinks actually fill
usable capacity.
ReleaseFast terminal benchmarks compare main with the combined map
changes:
| workload | before | after | speedup |
|---|---:|---:|---:|
| map churn | 1.253 s | 12.5 ms | 100x |
| full OSC 8 stream | 3.576 s | 75.6 ms | 47x |
| clear and redraw | 299.1 ms | 118.3 ms | 2.5x |
Co-authored-by: Tim Culverhouse <tim@timculverhouse.com>
