Wires the hs.3 runtime symbols (ailang_int_to_str, ailang_float_to_str)
into live AILang builtins. Four layers, one iter: checker install +
synth.rs lockstep partner; IR-header declares + Emitter::lower_app
arms (float arm replaces CodegenError::Internal, new int arm); rc.c
hoisted to unconditional link (weak attr on str.c's extern becomes
permanent no-op, retained intentionally); two new IR-shape pins + four
new E2E (two stdout-smoke, two RC-stats discipline) + drop.rs comment
refresh. Spec line refs were stale (hs.1+hs.2+hs.3 commits shifted
them); plan anchors to recon-verified positions lib.rs:1890-1903 and
:486-535. Edge cases (0, -1, i64::MAX, ±Inf, NaN) deferred to
follow-up tidy iter if regression sweep does not surface need.
Brummel
1f832c028a