fix(workflow): update STATE.md after discuss-phase completes (#556)

Add update_state step to record session info after context gathering,
matching the pattern used by execute-plan, add-todo, and other workflows.

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

get-shit-done/workflows/discuss-phase.md

@@ -394,6 +394,22 @@ node ~/.claude/get-shit-done/bin/gsd-tools.js commit "docs(${padded_phase}): cap
 Confirm: "Committed: docs(${padded_phase}): capture phase context"
 </step>
 
+<step name="update_state">
+Update STATE.md with session info:
+
+```bash
+node ~/.claude/get-shit-done/bin/gsd-tools.js state record-session \
+  --stopped-at "Phase ${PHASE} context gathered" \
+  --resume-file "${phase_dir}/${padded_phase}-CONTEXT.md"
+```
+
+Commit STATE.md:
+
+```bash
+node ~/.claude/get-shit-done/bin/gsd-tools.js commit "docs(state): record phase ${PHASE} context session" --files .planning/STATE.md
+```
+</step>
+
 </process>
 
 <success_criteria>
@@ -404,5 +420,6 @@ Confirm: "Committed: docs(${padded_phase}): capture phase context"
 - Scope creep redirected to deferred ideas
 - CONTEXT.md captures actual decisions, not vague vision
 - Deferred ideas preserved for future phases
+- STATE.md updated with session info
 - User knows next steps
 </success_criteria>