The hot control macros now live in the Clojure syntax tier. This was blocked
before: as interpreted overlay macros they re-expanded on every eval, timing out
a battery file (3930->3911). With the expand-once macro cache (prior commit) they
expand a single time with zero runtime cost, so moving them is free.
conformance 228/228 x3, clojure-test-suite 3930 (9 timeouts, not 10), full suite
green, bench flat (overlay vs janet macros within noise).
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