locals compares the frame on the stack against the body the session holds:
installing while stopped is allowed, so the two can be different bodies of
one function, and a rename that keeps the slot count pairs every name with
the wrong value. Emit.slot_fingerprint hashes each slot's name and type,
emit_fn puts it in the frame's static description, the agent reports it on
the backtrace line and Dev.locals compares it.
It does not fire. The test that drives it -- a redefinition that renames
every local of a function that is on the stack -- fails, and is committed
failing rather than deleted, because it is the only record of what is
wrong. Everything else in the suite is green; this one check is red.
It builds. See NEXT.md's handoff for where to look first.