Defines an optional top-level `spec_validation` profile section: a
registry mapping each markdown fence label to the tool that validates
a spec code block of that kind (`ext` + `cmd`, with a `{file}`
placeholder; exit 0 = clean parse, non-zero = BLOCK). Labels without an
entry are skipped-and-documented; a malformed entry fails closed.
This is P0 of issue #1 — the shared prerequisite for the brainstorm
Step-4 parse gate (Fix 1) and the grounding-check code-block pass
(Fix 2). Contract only; no consumer reads the slot yet.
refs #1
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Brummel
4a2c70baed