audit(specify): close cycle — repair planner, grounding-check, schema drift

Architect drift review (cycle 9e8b9ec..HEAD) returned drift_found. Three
cycle-introduced items, all repaired here as tidy edits:

- planner/SKILL.md: the cycle never touched it (recon never scoped it,
  the feat commit body's "every pipeline rendering agrees" over-claimed).
  Its Handoff Contract still named `brainstorm → planner` and the bounce
  `planner → brainstorm`; the Input-source cross-ref and two
  rationalisation rows still pointed at brainstorm as the spec producer.
  All repointed to specify (specify produces and owns the spec; brainstorm
  is the optional discovery stage upstream of it). The skip rule now lists
  specify in the design path tdd bypasses.
- specify/agents/grounding-check.md: the agent move left one stale pair —
  "self-review (Step 7) and user-approval (Step 8)" were brainstorm's old
  numbers; in specify they are Step 4 and Step 6.
- profile-schema + template: the `optional: true` per-phase key I
  introduced in the plan was undocumented AND rested on a semantic error —
  `brainstorm: { gates: [specify] }` reads as "specify cannot start until
  brainstorm has run", which is false (specify enters directly from
  sources). Corrected to `brainstorm: {}` (an active phase with no hard
  gate of its own, like implement); specify keeps `gates: [planner]` as
  the one real hard gate. The optional key is gone; brainstorm's
  optionality lives in the skip rules and SKILL prose, where it belongs.

Why these escaped the cycle's own grep suite: the consistency greps used
`brainstorm *-> *planner`, which does not match the real renderings
`` `brainstorm` -> `planner` `` (backticks between the words). The same
filter-string blind spot recurred twice this session; the verification
greps here tolerate optional backticks.

Pre-existing debt (NOT cycle-introduced), filed as backlog Brummel/Skills
issue #5 rather than fixed here: docs/migration.md's layout tree and
README's migration-status both predate tdd/glossary/pseudo/issue/
postmortem and misdescribe the roster.

Verdict: cycle drift-clean after these repairs (carry-on). No regression
gate (prose repo, no scripts). Not a milestone close.

docs/profile-schema.md

@@ -187,9 +187,7 @@ Per-phase configuration. Each phase has its own sub-map.
 
 ```yaml
 pipeline:
-  brainstorm:
-    gates: [specify]              # optional discovery; hands ratified design to specify
-    optional: true                # skipped when the design is settled in the sources
+  brainstorm: {}                  # optional discovery front-end; no hard gate of its own
   specify:
     gates: [planner]              # core node — planner cannot start until the spec is approved
   planner:
@@ -255,7 +253,7 @@ git:
     close_marker: "closes #N"
 
 pipeline:
-  brainstorm: { gates: [specify], optional: true }
+  brainstorm: {}                              # optional discovery; no hard gate
   specify:    { gates: [planner] }
   planner:    { gates: [implement] }
   implement:  {}