audit(specify): repair trailing brainstorm->specify doc drift

Follow-up to f775881. The architect's diff-scoped review missed four
prose references outside the cycle diff that the brainstorm shrink left
stale — the aspirational-marker and parse-gate machinery moved to specify
(it writes the spec and runs the gates), but these still said brainstorm:

- profile-schema.md aspirational-source section: "a later brainstorm
  tell aspirational content", "the brainstorm degrades", "consumed by
  the brainstorm skill", and the "Step-7 parse-every-block gate" number
  (specify's parse gate is Step 4, not Step 7).
- profile-schema.md spec_validation section: "The brainstorm parse-gate".
- README "Retrofitting spec_validation": "brainstorm Step 7 self-review"
  -> "specify Step 4 self-review".

Found by sweeping every brainstorm reference in the two files for ones
that describe spec-production rather than discovery. planner Step 5
self-review and the grounding-check pass references were already correct.

README.md

@@ -117,7 +117,7 @@ the tool that validates a spec code block of that kind. It powers
 the parse gates that stop a spec from shipping code blocks that do
 not parse against the live tool:
 
-- `brainstorm` Step 7 self-review — the parse-every-block gate
+- `specify` Step 4 self-review — the parse-every-block gate
 - `planner` Step 5 self-review — the parse-the-bytes-you-inline gate
 - the `grounding-check` agent's code-block parse pass