feat: add /gsd:debug for systematic debugging with persistent state

- Creates .planning/debug/[slug].md immediately on command
- Continuous updates: file IS the debugging brain
- Clear section rules: OVERWRITE (Current Focus, Resolution) vs APPEND (Evidence, Eliminated)
- Survives /clear perfectly - resume from any interruption point
- Scientific method: evidence → hypothesis → test → eliminate or confirm
- Includes debugging reference files (mindset, hypothesis testing, investigation techniques)

Closes #53, closes #44

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

commands/gsd/debug.md

@@ -0,0 +1,58 @@
+---
+name: gsd:debug
+description: Systematic debugging with persistent state across context resets
+argument-hint: [issue description]
+allowed-tools:
+  - Read
+  - Write
+  - Edit
+  - Bash
+  - Grep
+  - Glob
+  - AskUserQuestion
+---
+
+<objective>
+Debug issues using scientific method with a persistent debug document that survives `/clear`.
+
+If resuming (no arguments and active session exists): pick up where you left off.
+If starting new: gather symptoms, then investigate autonomously.
+</objective>
+
+<execution_context>
+@~/.claude/get-shit-done/workflows/debug.md
+@~/.claude/get-shit-done/templates/DEBUG.md
+</execution_context>
+
+<context>
+User's issue: $ARGUMENTS
+
+Check for active debug sessions:
+```bash
+ls .planning/debug/*.md 2>/dev/null | head -5
+```
+</context>
+
+<process>
+Follow the workflow in @~/.claude/get-shit-done/workflows/debug.md
+
+**Quick reference:**
+
+1. **Check for active sessions** - Offer to resume or start new
+2. **Gather symptoms** - What happened? What should happen? Errors? When?
+3. **Create DEBUG.md** - Document symptoms in `.planning/debug/[slug].md`
+4. **Investigate** - Evidence → Hypothesis → Test → Eliminate or Confirm
+5. **Fix and verify** - Minimal fix, verify against original symptoms
+6. **Archive** - Move to `.planning/debug/resolved/`
+
+**Key principle:** The DEBUG.md is your memory. Update it constantly. It survives `/clear`.
+</process>
+
+<success_criteria>
+- [ ] Active sessions checked before starting new
+- [ ] Symptoms gathered through AskUserQuestion (not inline questions)
+- [ ] DEBUG.md tracks all investigation state
+- [ ] Scientific method followed (not random fixes)
+- [ ] Root cause confirmed with evidence before fixing
+- [ ] Fix verified and session archived
+</success_criteria>

commands/gsd/help.md

@@ -248,6 +248,20 @@ Review deferred issues with codebase context.
 
 Usage: `/gsd:consider-issues`
 
+### Debugging
+
+**`/gsd:debug [issue description]`**
+Systematic debugging with persistent state across context resets.
+
+- Gathers symptoms through adaptive questioning
+- Creates `.planning/debug/[slug].md` to track investigation
+- Investigates using scientific method (evidence → hypothesis → test)
+- Survives `/clear` — run `/gsd:debug` with no args to resume
+- Archives resolved issues to `.planning/debug/resolved/`
+
+Usage: `/gsd:debug "login button doesn't work"`
+Usage: `/gsd:debug` (resume active session)
+
 ### Todo Management
 
 **`/gsd:add-todo [description]`**
@@ -291,6 +305,8 @@ Show this command reference.
 ├── todos/                # Captured ideas and tasks
 │   ├── pending/          # Todos waiting to be worked on
 │   └── done/             # Completed todos
+├── debug/                # Active debug sessions
+│   └── resolved/         # Archived resolved issues
 ├── codebase/             # Codebase map (brownfield projects)
 │   ├── STACK.md          # Languages, frameworks, dependencies
 │   ├── ARCHITECTURE.md   # Patterns, layers, data flow
@@ -367,6 +383,15 @@ Change anytime by editing `.planning/config.json`
 /gsd:check-todos api             # Filter by area
 ```
 
+**Debugging an issue:**
+
+```
+/gsd:debug "form submission fails silently"  # Start debug session
+# ... investigation happens, context fills up ...
+/clear
+/gsd:debug                                    # Resume from where you left off
+```
+
 ## Getting Help
 
 - Read `.planning/PROJECT.md` for project vision

commands/gsd/progress.md

@@ -58,6 +58,7 @@ If missing STATE.md or ROADMAP.md: inform what's missing, suggest running `/gsd:
 - Note any blockers, concerns, or deferred issues
 - Check for CONTEXT.md: For phases without PLAN.md files, check if `{phase}-CONTEXT.md` exists in phase directory
 - Count pending todos: `ls .planning/todos/pending/*.md 2>/dev/null | wc -l`
+- Check for active debug sessions: `ls .planning/debug/*.md 2>/dev/null | grep -v resolved | wc -l`
   </step>
 
 <step name="report">
@@ -87,6 +88,10 @@ CONTEXT: [✓ if CONTEXT.md exists | - if not]
 ## Pending Todos
 - [count] pending — /gsd:check-todos to review
 
+## Active Debug Sessions
+- [count] active — /gsd:debug to continue
+(Only show this section if count > 0)
+
 ## What's Next
 [Next phase/plan objective from ROADMAP]
 ```