Brummel
8bfa09adc7
Six tasks: (1) runtime C functions in runtime/str.c, (2) builtin install lockstep across builtins.rs + synth.rs + list() row + 2 unit tests, (3) codegen IR wiring (2 declares + 2 lower_app arms + is_static_callee whitelist), (4) 2 IR-shape unit pins, (5) regen 5 IR snapshots, (6) 4 fixtures + 5 E2E tests + acceptance gate. Mechanical mirror of hs.4's int_to_str/float_to_str pattern. Plan captures every Edit verbatim (old_string + new_string) per planner Iron Law. Pre-existing drift fix included inline: int_to_str row missing from builtins.rs::list() since hs.4 — adding it adjacent to the two new rows. Three open questions from plan-recon resolved by Boss judgement (C uses bool from <stdbool.h>; tests live in crates/ail/tests/e2e.rs as the existing real path; int_to_str list() row drift fixed inline).