Closes#94.
Generates the racial radial rows at build time from the `UsableFeat` column in the race feats tables, replacing the hand-maintained racial block in `sow-topdata` `data/classes/feats/global.json`.
## Why
Racial spell-like abilities reach the in-game radial only via an `OnMenu` row in every `cls_feat_<class>.2da`. Racial feats are granted by race, never by a class, so nothing adds them automatically — they were hand-written and prepended into every class table. The list drifts: this build already had **24** usable racial feats in the race tables but only **23** hand rows, so one activatable feat was silently missing.
## What
- `racialUsableFeatRules()` scans `race_feat_*.2da` datasets, collects `UsableFeat=1` feats, emits one rule each: `List=3, GrantedOnLevel=99, OnMenu=1`. Deduped across races, sorted for deterministic output.
- Row shape is exactly the in-game-verified hand rows. `List=3` keeps it off every level-up selection list; `GrantedOnLevel=99` is above the level cap so no class ever actually grants it (`nLevelGranted` is `uint8_t`); `OnMenu=1` renders the button once the creature possesses the feat. Possession stays chargen / the login racial-feat sync (`sow-codebase#359`).
- Reuses the existing `globalRules` injection path (same dedup, feat-existence check, label lookup) but applies **unconditionally**, so a leftover hand row in `global.json` deduplicates to a no-op — the `sow-topdata` cleanup lands separately.
- Not sourced from `feat.2da`: a global feat flag would inject unrelated class abilities (e.g. a shadowdancer ability) into every class radial via multiclass.
## Tests
- `racial_feat_rules_test.go`: usable-only, non-usable excluded, cross-race dedup, non-`race_feat_` ignored, deterministic order.
- Existing `cls_feat` global-injection build tests still pass with the new parameter.
- End-to-end: with the racial block removed from `global.json`, a real `build-topdata` emits `TieflingDarkness 3 99 1` once per table across all 21, 24 racial rows total.
## Merge order
The `sow-topdata` `global.json` racial-row deletion depends on this — it must ship first (or the racial radial vanishes on the next topdata build with the released tool).
🤖 Generated with [Claude Code](https://claude.com/claude-code)Reviewed-on: #95
Co-authored-by: vickydotbat <vickydotbat@tutamail.com>
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