feat: add /gsd:ui-phase + /gsd:ui-review design contract and visual audit layer (closes #986)

Add pre-planning design contract generation and post-execution visual audit
for frontend phases. Closes the gap where execute-phase runs without a visual
contract, producing inconsistent spacing, color, and typography across components.

New agents: gsd-ui-researcher (UI-SPEC.md), gsd-ui-checker (6-dimension
validation), gsd-ui-auditor (6-pillar scored audit + registry re-vetting).
Third-party shadcn registry blocks are machine-vetted at contract time,
verification time, and audit time — three enforcement points, not a checkbox.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

commands/gsd/ui-phase.md

@@ -0,0 +1,34 @@
+---
+name: gsd:ui-phase
+description: Generate UI design contract (UI-SPEC.md) for frontend phases
+argument-hint: "[phase]"
+allowed-tools:
+  - Read
+  - Write
+  - Bash
+  - Glob
+  - Grep
+  - Task
+  - WebFetch
+  - AskUserQuestion
+  - mcp__context7__*
+---
+<objective>
+Create a UI design contract (UI-SPEC.md) for a frontend phase.
+Orchestrates gsd-ui-researcher and gsd-ui-checker.
+Flow: Validate → Research UI → Verify UI-SPEC → Done
+</objective>
+
+<execution_context>
+@~/.claude/get-shit-done/workflows/ui-phase.md
+@~/.claude/get-shit-done/references/ui-brand.md
+</execution_context>
+
+<context>
+Phase number: $ARGUMENTS — optional, auto-detects next unplanned phase if omitted.
+</context>
+
+<process>
+Execute @~/.claude/get-shit-done/workflows/ui-phase.md end-to-end.
+Preserve all workflow gates.
+</process>

commands/gsd/ui-review.md

@@ -0,0 +1,32 @@
+---
+name: gsd:ui-review
+description: Retroactive 6-pillar visual audit of implemented frontend code
+argument-hint: "[phase]"
+allowed-tools:
+  - Read
+  - Write
+  - Bash
+  - Glob
+  - Grep
+  - Task
+  - AskUserQuestion
+---
+<objective>
+Conduct a retroactive 6-pillar visual audit. Produces UI-REVIEW.md with
+graded assessment (1-4 per pillar). Works on any project.
+Output: {phase_num}-UI-REVIEW.md
+</objective>
+
+<execution_context>
+@~/.claude/get-shit-done/workflows/ui-review.md
+@~/.claude/get-shit-done/references/ui-brand.md
+</execution_context>
+
+<context>
+Phase: $ARGUMENTS — optional, defaults to last completed phase.
+</context>
+
+<process>
+Execute @~/.claude/get-shit-done/workflows/ui-review.md end-to-end.
+Preserve all workflow gates.
+</process>