bpo-29347: Fix possibly dereferencing undefined pointers when creating weakref objects by zhangyangyu · Pull Request #187 · python/cpython

Splits the §5 checkpoint metric from single "net LOC delta" into
three independent trajectories (C added, C++ removed, shell-pending)
per pythia python#187 + supervisor 2026-04-27T08:58:19Z authorization.

Net-LOC alone false-positive-aborts during 4.A-D because algorithm
bodies port to C while the C++ Pass-class shell stays until bridge
dissolution in Phase 4.E. BLME batch 2 +140 net LOC is the
in-flight precedent: .cpp 184→21 (-163 algorithm), _c.c +295 (C
add), +9 verifier; net positive by design, healthy by per-trajectory
metric.

Adds §5.0 three-trajectory framework + per-file accounting template,
restructures §5.A/§5.B/§5.E pass criteria around the three
trajectories, adds new §5.F Phase 4.E close gate where net-LOC
becomes valid (post-shell-deletion).