fix: capture dev story baseline commits (#2403)

Co-authored-by: Brian <bmadcode@gmail.com>

src/bmm-skills/4-implementation/bmad-dev-story/SKILL.md

@@ -10,7 +10,7 @@ description: 'Execute story implementation following a context filled story spec
 **Your Role:** Developer implementing the story.
 - Communicate all responses in {communication_language} and language MUST be tailored to {user_skill_level}
 - Generate all documents in {document_output_language}
-- Only modify the story file in these areas: Tasks/Subtasks checkboxes, Dev Agent Record (Debug Log, Completion Notes), File List, Change Log, and Status
+- Only modify the story file in these areas: YAML frontmatter `baseline_commit`, Tasks/Subtasks checkboxes, Dev Agent Record (Debug Log, Completion Notes), File List, Change Log, and Status
 - Execute ALL steps in exact order; do NOT skip steps
 - Absolutely DO NOT stop because of "milestones", "significant progress", or "session boundaries". Continue in a single execution until the story is COMPLETE (all ACs satisfied and all tasks/subtasks checked) UNLESS a HALT condition is triggered or the USER gives other instruction.
 - Do NOT schedule a "next session" or request review pauses unless a HALT condition applies. Only Step 9 decides completion.
@@ -76,7 +76,7 @@ Activation is complete. If `activation_steps_prepend` or `activation_steps_appen
 <workflow>
   <critical>Communicate all responses in {communication_language} and language MUST be tailored to {user_skill_level}</critical>
   <critical>Generate all documents in {document_output_language}</critical>
-  <critical>Only modify the story file in these areas: Tasks/Subtasks checkboxes, Dev Agent Record (Debug Log, Completion Notes), File List,
+  <critical>Only modify the story file in these areas: YAML frontmatter `baseline_commit`, Tasks/Subtasks checkboxes, Dev Agent Record (Debug Log, Completion Notes), File List,
     Change Log, and Status</critical>
   <critical>Execute ALL steps in exact order; do NOT skip steps</critical>
   <critical>Absolutely DO NOT stop because of "milestones", "significant progress", or "session boundaries". Continue in a single execution
@@ -261,26 +261,40 @@ Activation is complete. If `activation_steps_prepend` or `activation_steps_appen
   </step>
 
   <step n="4" goal="Mark story in-progress" tag="sprint-status">
+    <action>If story file YAML frontmatter already contains `baseline_commit`, preserve the existing value and do not overwrite it</action>
+
     <check if="{{sprint_status}} file exists">
       <action>Load the FULL file: {{sprint_status}}</action>
       <action>Read all development_status entries to find {{story_key}}</action>
-      <action>Get current status value for development_status[{{story_key}}]</action>
+      <action>Set {{current_status}} to development_status[{{story_key}}]</action>
+    </check>
 
-      <check if="current status == 'ready-for-dev' OR review_continuation == true">
+    <check if="{{sprint_status}} file does NOT exist">
+      <action>Set {{current_status}} to the story file Status section value</action>
+    </check>
+
+    <check if="{{current_status}} == 'ready-for-dev' AND story file YAML frontmatter does NOT contain baseline_commit">
+      <action>Run `git rev-parse HEAD` to capture current commit into {{baseline_commit}}; if git/version control is unavailable, set {{baseline_commit}} = `NO_VCS`</action>
+      <action>If story file YAML frontmatter exists, add `baseline_commit: {{baseline_commit}}` to the frontmatter</action>
+      <action>If story file has no YAML frontmatter, create frontmatter at the top containing only `baseline_commit: {{baseline_commit}}`</action>
+    </check>
+
+    <check if="{{sprint_status}} file exists">
+      <check if="{{current_status}} == 'ready-for-dev' OR (review_continuation == true AND {{current_status}} != 'in-progress')">
         <action>Update the story in the sprint status report to = "in-progress"</action>
         <action>Update last_updated field to current date</action>
         <output>🚀 Starting work on story {{story_key}}
-          Status updated: ready-for-dev → in-progress
+          Status updated: {{current_status}} → in-progress
         </output>
       </check>
 
-      <check if="current status == 'in-progress'">
+      <check if="{{current_status}} == 'in-progress'">
         <output>⏯️ Resuming work on story {{story_key}}
           Story is already marked in-progress
         </output>
       </check>
 
-      <check if="current status is neither ready-for-dev nor in-progress">
+      <check if="{{current_status}} is neither ready-for-dev nor in-progress">
         <output>⚠️ Unexpected story status: {{current_status}}
           Expected ready-for-dev or in-progress. Continuing anyway...
         </output>