Guard C-family header changes from active overlay publication until active edge parity is proven against fresh rebuilds. Bounded header edits can still use exact base-delta publication, preserving correctness without forcing every safe case to full rebuild.
Add a focused C-header incremental canary that verifies no overlay publish, exact frontier expansion, exact publish stats, and fresh-rebuild equality. Clean up stale direct-frontier helper code from the failed cap64 overlay experiment.
Validation: CBM_ONLY_SUITE=pipeline build/c/test-runner -> 323 passed; make -f Makefile.cbm lint-source-safety -> OK; self-dogfood cap16/cap64 store_pipeline_batch passed canonical equality but still fell back with frontier_too_large at 2.81x/2.74x.
Signed-off-by: Andrew Hundt <ATHundt@gmail.com>
Andrew Hundt
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