chore(#1867): register ui-consideration probe + regen install cascade (SHIP-01)

Ship-safe registration + regenerated snapshots for the #1867 UI-consideration
probe (Phase 3, SHIP-01):

- CONTEXT.md: PROBE.ui.{verification,axis,seam} predicates + ui-consideration
  -probe added to PROBE.family (machine-canon for the 3rd adapter, MIXED axis).
- agents/gsd-ui-{researcher,checker}.md: one @-include of
  references/ui-consideration-probe.md each (both under the 24576 agent cap).
- docs/INVENTORY.md + INVENTORY-MANIFEST.json: register the reference doc and
  the compiled ui-consideration-probe.cjs (inventory-manifest-sync green).
- tests/fixtures/golden-install-parity/*.json (16 runtimes): recaptured against
  a clean full build — folds in the deferred Phase-1 (ref doc, plan-phase lift)
  and Phase-2 (ui-phase step, UI-SPEC section) install-surface changes.
- tests/agent-size-baseline.json: ratcheted the two grown UI agents.
- .changeset/vivid-orcas-chatter.md: type Added (pr updated at PR-open).

Inventory/golden/size gates green; lint:ci + lint:docs + lint:changeset green.
The plan-phase.md PRE_PHASE6 ceiling stays RED pending #1852 (unchanged).

Claude-Session: https://claude.ai/code/session_01BKt4hgNZwXSeJYJtYAQUSS

.changeset/vivid-orcas-chatter.md

@@ -0,0 +1,5 @@
+---
+type: Added
+pr: 1867
+---
+**`/gsd-ui-phase` now probes UI state coverage** — a new `ui-consideration-probe` (the third `probe-core` adapter) enumerates the shape-rooted UI states a UI-SPEC must resolve (empty/loading/error/populated/partial/overflow/zero-one-many/long-text). After the UI checker approves, the probe surfaces applicable considerations for each element, records a `## UI Considerations` section in the UI-SPEC, and plan-phase lifts each resolved consideration into `must_haves` — so a purely-visual state with no wired test routes to `insufficient_spec → human_needed` at verify rather than a silent pass.