ref-allow hygiene: fan_race_mapper's rung-floor mirror added, three stale ±0 directives removed

[O6lvl4]

Judging the released v0.61.0 binary against the frozen corpus surfaced one FAIL and three STALE rows on the ref leg — all four are directive hygiene, not implementation defects:

• spec/wasm_cross/fan_race_mapper.almd: the fixture has documented its native rung-floor wall via @xt-allow since v0.5x, but the ref leg (TOR-8, landed 2026-08-21) consults only @ref-allow — so ref-vs-native reported a disagreement that is in fact the same adjudicated divergence. The @ref-allow mirror is added with the same reason; ref and wasm agree byte-for-byte. v0.59.2 walls identically, so this is not a 0.60/0.61 regression.
• Three ±0 float fixtures: their @ref-allow directives went stale the day v0.59.2 shipped the ALS-T23 tie fix — the legs now MATCH the reference. Removed per the runner's own stale flag (shrink direction).

After this change, the full run against v0.61.0: diag 779/779, fail green, ref 611 judged / 0 abstained / 2 tracked allows / 0 stale / 0 failed — ALS conformance: PASS.

Follow-up filed separately: edition-readiness runs only the runner selftest, never the corpus against a binary, which is how the fan_race_mapper row stayed invisible at the v1.0.0 tag.

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