Bootstrap seed 8/8: restore safe free — chain tip (d5bae558)

Bootstrap seed — Linux x86_64 stage3 @ d5bae558 (chain rung 8 / 8 — chain tip)

This asset is the Linux x86_64 self-hosted with compiler (a stage3 build)
at commit d5bae5587f60b4a8afd6cb26cef288d11be127e7 — the tip of master.

• Commit: d5bae558 — rt: restore safe free — NEVER_FREE_MODE 1 -> 0
• Role: rung 8 of 8 — restores real free(). This is the endpoint the whole
  chain exists to reach: the D22 map-view flip landed and memory is freed for
  real, with no double-free.
• Predecessor seed: rung 7 (9afc7d71) stage3.
• What it changes: flips NEVER_FREE_MODE from 1 back to 0 in rt/rt_core.w.
  With rung 7's deep-copy fix in place, the compiler compiles all ~26k lines of
  itself with real free() and no double-free.
• Verification: re-verified this cycle — seeded from rung 7, full
  stage1/2/3 build, byte-identical fixpoint (stage2 == stage3),
  sha256 = 2723fa24cd60aa96c5d9f6586f3da3393c95a8c7f8487894ba1d5c1079b40743
  (this asset). Determinism cross-check: the same tip stage3 is produced whether
  seeded from rung 7 or directly from rung 6 — the safe-free tip is a stable
  fixed point. This is the seed the Linux CI bootstrap pulls in.

Asset: with-linux-x86_64 (+ .sha256). Use as a bootstrap seed:
WITH=./with-linux-x86_64 with build :stage1 (needs the pinned LLVM SDK in .deps/).