feat: add /gsd-spec-phase — Socratic spec refinement with ambiguity scoring (#2213) (#2322)

Introduces `/gsd-spec-phase <phase>` as an optional pre-step before discuss-phase.
Clarifies WHAT a phase delivers (requirements, boundaries, acceptance criteria) with
quantitative ambiguity scoring before discuss-phase handles HOW to implement.

- `commands/gsd/spec-phase.md` — slash command routing to workflow
- `get-shit-done/workflows/spec-phase.md` — full Socratic interview loop (up to 6
  rounds, 5 rotating perspectives: Researcher, Simplifier, Boundary Keeper, Failure
  Analyst, Seed Closer) with weighted 4-dimension ambiguity gate (≤ 0.20 to write SPEC.md)
- `get-shit-done/templates/spec.md` — SPEC.md template with falsifiable requirements
  (Current/Target/Acceptance per requirement), Boundaries, Acceptance Criteria,
  Ambiguity Report, and Interview Log; includes two full worked examples
- `get-shit-done/workflows/discuss-phase.md` — new `check_spec` step detects
  `{padded_phase}-SPEC.md` at startup; displays "Found SPEC.md — N requirements
  locked. Focusing on implementation decisions."; `analyze_phase` respects `spec_loaded`
  flag to skip "what/why" gray areas; `write_context` emits `<spec_lock>` section
  with boundary summary and canonical ref to SPEC.md
- `docs/ARCHITECTURE.md` — update command/workflow counts (74→75, 71→72)

Closes #2213

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

docs/ARCHITECTURE.md

@@ -113,7 +113,7 @@ User-facing entry points. Each file contains YAML frontmatter (name, description
 - **Copilot:** Slash commands (`/gsd-command-name`)
 - **Antigravity:** Skills
 
-**Total commands:** 74
+**Total commands:** 75
 
 ### Workflows (`get-shit-done/workflows/*.md`)
 
@@ -124,7 +124,7 @@ Orchestration logic that commands reference. Contains the step-by-step process i
 - State update patterns
 - Error handling and recovery
 
-**Total workflows:** 71
+**Total workflows:** 72
 
 ### Agents (`agents/*.md`)
 
@@ -409,11 +409,11 @@ UI-SPEC.md (per phase) ───────────────────
 
 ```
 ~/.claude/                          # Claude Code (global install)
-├── commands/gsd/*.md               # 74 slash commands
+├── commands/gsd/*.md               # 75 slash commands
 ├── get-shit-done/
 │   ├── bin/gsd-tools.cjs           # CLI utility
 │   ├── bin/lib/*.cjs               # 19 domain modules
-│   ├── workflows/*.md              # 71 workflow definitions
+│   ├── workflows/*.md              # 72 workflow definitions
 │   ├── references/*.md             # 35 shared reference docs
 │   └── templates/                  # Planning artifact templates
 ├── agents/*.md                     # 31 agent definitions