Root cause: context called inside lambdas (e.g. swap!) went through
nested cek_run with empty kont, so provide frames weren't found and
never tracked to *bind-tracking*.
Three changes in evaluator.sx:
- step-sf-context: track context names (not frames) to *bind-tracking*
— names work across cek_run boundaries via scope-peek fallback
- bind continue: resolve tracked names to frames via kont-find-provide
on rest-k before registering subscribers
- subscriber: use empty kont instead of kont-extract-provides — old
approach created provide frames whose continue handlers called
scope-pop!, corrupting the scope stack
2752/2768 OCaml tests pass (all 7 bind subscriber tests fixed).
32/32 WASM native tests pass.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>