fix(git): correct has_changes detection and dependency handling

- git-analyze-changes: check actual diff content instead of command success
- git-commit: make stage_files dependency optional to allow analyzing pre-staged files

Author: ibacalu

src/workflows_mcp/templates/git/git-analyze-changes.yaml

@@ -110,7 +110,7 @@ blocks:
 
 outputs:
   has_changes:
-    value: "{{blocks.get_staged_diff.succeeded or blocks.get_all_diff.succeeded}}"
+    value: "{{blocks.processing.outputs.diff | trim | length > 0}}"
     type: bool
   summary:
     value: "{{blocks.processing.outputs.summary}}"

src/workflows_mcp/templates/git/git-commit.yaml

@@ -56,7 +56,9 @@ blocks:
   - id: analyze_changes
     type: Workflow
     description: "Analyze staged changes in git repository"
-    depends_on: [stage_files]
+    depends_on:
+      - block: stage_files
+        required: false
     inputs:
       workflow: "git-analyze-changes"
       inputs: