fix(phase): add ROADMAP.md fallback to cmdPhaseComplete next-phase scan

cmdPhaseComplete determines is_last_phase and next_phase by scanning
.planning/phases/ directories on disk. Phases defined in ROADMAP.md
but not yet planned (no directory created) are invisible to this scan,
causing premature is_last_phase:true when only the first phase has
been scaffolded.

Add a fallback that parses ROADMAP.md phase headings when the
filesystem scan finds no next phase. Uses the existing comparePhaseNum
utility for consistent ordering with letter suffixes and decimals.

Closes #709

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

get-shit-done/bin/lib/phase.cjs

@@ -783,7 +783,9 @@ function cmdPhaseComplete(cwd, phaseNum, raw) {
     }
   }
 
-  // Find next phase
+  // Find next phase — check both filesystem AND roadmap
+  // Phases may be defined in ROADMAP.md but not yet scaffolded to disk,
+  // so a filesystem-only scan would incorrectly report is_last_phase:true
   let nextPhaseNum = null;
   let nextPhaseName = null;
   let isLastPhase = true;
@@ -806,6 +808,24 @@ function cmdPhaseComplete(cwd, phaseNum, raw) {
     }
   } catch {}
 
+  // Fallback: if filesystem found no next phase, check ROADMAP.md
+  // for phases that are defined but not yet planned (no directory on disk)
+  if (isLastPhase && fs.existsSync(roadmapPath)) {
+    try {
+      const roadmapForPhases = fs.readFileSync(roadmapPath, 'utf-8');
+      const phasePattern = /#{2,4}\s*Phase\s+(\d+[A-Z]?(?:\.\d+)*)\s*:\s*([^\n]+)/gi;
+      let pm;
+      while ((pm = phasePattern.exec(roadmapForPhases)) !== null) {
+        if (comparePhaseNum(pm[1], phaseNum) > 0) {
+          nextPhaseNum = pm[1];
+          nextPhaseName = pm[2].replace(/\(INSERTED\)/i, '').trim().toLowerCase().replace(/\s+/g, '-');
+          isLastPhase = false;
+          break;
+        }
+      }
+    } catch {}
+  }
+
   // Update STATE.md
   if (fs.existsSync(statePath)) {
     let stateContent = fs.readFileSync(statePath, 'utf-8');