fix(core): extend atomicWriteFileSync to milestone, phase, and frontmatter (#1972)

Replace 11 fs.writeFileSync calls with atomicWriteFileSync in three
files that write to .planning/ artifacts (ROADMAP.md, REQUIREMENTS.md,
MILESTONES.md, and frontmatter updates). This prevents partial writes
from corrupting planning files on crash or power loss.

Skipped low-risk writes: .gitkeep (empty files) and archive directory
writes (new files, not read-modify-write).

Files changed:
- milestone.cjs: 5 sites (REQUIREMENTS.md, MILESTONES.md)
- phase.cjs: 5 sites (ROADMAP.md, REQUIREMENTS.md)
- frontmatter.cjs: 2 sites (arbitrary .planning/ files)

Closes #1972

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

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

@@ -4,7 +4,7 @@
 
 const fs = require('fs');
 const path = require('path');
-const { safeReadFile, normalizeMd, output, error } = require('./core.cjs');
+const { safeReadFile, normalizeMd, output, error, atomicWriteFileSync } = require('./core.cjs');
 
 // ─── Parsing engine ───────────────────────────────────────────────────────────
 
@@ -337,7 +337,7 @@ function cmdFrontmatterSet(cwd, filePath, field, value, raw) {
   try { parsedValue = JSON.parse(value); } catch { parsedValue = value; }
   fm[field] = parsedValue;
   const newContent = spliceFrontmatter(content, fm);
-  fs.writeFileSync(fullPath, normalizeMd(newContent), 'utf-8');
+  atomicWriteFileSync(fullPath, normalizeMd(newContent));
   output({ updated: true, field, value: parsedValue }, raw, 'true');
 }
 
@@ -351,7 +351,7 @@ function cmdFrontmatterMerge(cwd, filePath, data, raw) {
   try { mergeData = JSON.parse(data); } catch { error('Invalid JSON for --data'); return; }
   Object.assign(fm, mergeData);
   const newContent = spliceFrontmatter(content, fm);
-  fs.writeFileSync(fullPath, normalizeMd(newContent), 'utf-8');
+  atomicWriteFileSync(fullPath, normalizeMd(newContent));
   output({ merged: true, fields: Object.keys(mergeData) }, raw, 'true');
 }
 

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

@@ -4,7 +4,7 @@
 
 const fs = require('fs');
 const path = require('path');
-const { escapeRegex, getMilestonePhaseFilter, extractOneLinerFromBody, normalizeMd, planningPaths, output, error } = require('./core.cjs');
+const { escapeRegex, getMilestonePhaseFilter, extractOneLinerFromBody, normalizeMd, planningPaths, output, error, atomicWriteFileSync } = require('./core.cjs');
 const { extractFrontmatter } = require('./frontmatter.cjs');
 const { writeStateMd, stateReplaceFieldWithFallback } = require('./state.cjs');
 
@@ -74,7 +74,7 @@ function cmdRequirementsMarkComplete(cwd, reqIdsRaw, raw) {
   }
 
   if (updated.length > 0) {
-    fs.writeFileSync(reqPath, reqContent, 'utf-8');
+    atomicWriteFileSync(reqPath, reqContent);
   }
 
   output({
@@ -178,21 +178,21 @@ function cmdMilestoneComplete(cwd, version, options, raw) {
     const existing = fs.readFileSync(milestonesPath, 'utf-8');
     if (!existing.trim()) {
       // Empty file — treat like new
-      fs.writeFileSync(milestonesPath, normalizeMd(`# Milestones\n\n${milestoneEntry}`), 'utf-8');
+      atomicWriteFileSync(milestonesPath, normalizeMd(`# Milestones\n\n${milestoneEntry}`));
     } else {
       // Insert after the header line(s) for reverse chronological order (newest first)
       const headerMatch = existing.match(/^(#{1,3}\s+[^\n]*\n\n?)/);
       if (headerMatch) {
         const header = headerMatch[1];
         const rest = existing.slice(header.length);
-        fs.writeFileSync(milestonesPath, normalizeMd(header + milestoneEntry + rest), 'utf-8');
+        atomicWriteFileSync(milestonesPath, normalizeMd(header + milestoneEntry + rest));
       } else {
         // No recognizable header — prepend the entry
-        fs.writeFileSync(milestonesPath, normalizeMd(milestoneEntry + existing), 'utf-8');
+        atomicWriteFileSync(milestonesPath, normalizeMd(milestoneEntry + existing));
       }
     }
   } else {
-    fs.writeFileSync(milestonesPath, normalizeMd(`# Milestones\n\n${milestoneEntry}`), 'utf-8');
+    atomicWriteFileSync(milestonesPath, normalizeMd(`# Milestones\n\n${milestoneEntry}`));
   }
 
   // Update STATE.md — use shared helpers that handle both **bold:** and plain Field: formats

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

@@ -4,7 +4,7 @@
 
 const fs = require('fs');
 const path = require('path');
-const { escapeRegex, loadConfig, normalizePhaseName, comparePhaseNum, findPhaseInternal, getArchivedPhaseDirs, generateSlugInternal, getMilestonePhaseFilter, stripShippedMilestones, extractCurrentMilestone, replaceInCurrentMilestone, toPosixPath, planningDir, withPlanningLock, output, error, readSubdirectories, phaseTokenMatches } = require('./core.cjs');
+const { escapeRegex, loadConfig, normalizePhaseName, comparePhaseNum, findPhaseInternal, getArchivedPhaseDirs, generateSlugInternal, getMilestonePhaseFilter, stripShippedMilestones, extractCurrentMilestone, replaceInCurrentMilestone, toPosixPath, planningDir, withPlanningLock, output, error, readSubdirectories, phaseTokenMatches, atomicWriteFileSync } = require('./core.cjs');
 const { extractFrontmatter } = require('./frontmatter.cjs');
 const { writeStateMd, readModifyWriteStateMd, stateExtractField, stateReplaceField, stateReplaceFieldWithFallback, updatePerformanceMetricsSection } = require('./state.cjs');
 
@@ -392,7 +392,7 @@ function cmdPhaseAdd(cwd, description, raw, customId) {
       updatedContent = rawContent + phaseEntry;
     }
 
-    fs.writeFileSync(roadmapPath, updatedContent, 'utf-8');
+    atomicWriteFileSync(roadmapPath, updatedContent);
     return { newPhaseId: _newPhaseId, dirName: _dirName };
   });
 
@@ -493,7 +493,7 @@ function cmdPhaseInsert(cwd, afterPhase, description, raw) {
     }
 
     const updatedContent = rawContent.slice(0, insertIdx) + phaseEntry + rawContent.slice(insertIdx);
-    fs.writeFileSync(roadmapPath, updatedContent, 'utf-8');
+    atomicWriteFileSync(roadmapPath, updatedContent);
     return { decimalPhase: _decimalPhase, dirName: _dirName };
   });
 
@@ -607,7 +607,7 @@ function updateRoadmapAfterPhaseRemoval(roadmapPath, targetPhase, isDecimal, rem
       }
     }
 
-    fs.writeFileSync(roadmapPath, content, 'utf-8');
+    atomicWriteFileSync(roadmapPath, content);
   });
 }
 
@@ -783,7 +783,7 @@ function cmdPhaseComplete(cwd, phaseNum, raw) {
         roadmapContent = roadmapContent.replace(planCheckboxPattern, '$1x$2');
       }
 
-      fs.writeFileSync(roadmapPath, roadmapContent, 'utf-8');
+      atomicWriteFileSync(roadmapPath, roadmapContent);
 
       // Update REQUIREMENTS.md traceability for this phase's requirements
       const reqPath = path.join(planningDir(cwd), 'REQUIREMENTS.md');
@@ -816,7 +816,7 @@ function cmdPhaseComplete(cwd, phaseNum, raw) {
             );
           }
 
-          fs.writeFileSync(reqPath, reqContent, 'utf-8');
+          atomicWriteFileSync(reqPath, reqContent);
           requirementsUpdated = true;
         }
       }