fix(bmm): remove stale validate-prd references (fixes #1030) (#1038)

- Remove validate-prd workflow references from all workflow path YAML files
- Update Excalidraw diagram: remove Validate PRD box and zombie JSON elements
- Re-export SVG at 1x scale
- Standardize implementation-readiness descriptions across all docs
- Add validation script (validate-svg-changes.sh) and README for SVG export process
- Correct Excalidraw timestamps

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/modules/bmm/docs/images/README.md

@@ -0,0 +1,37 @@
+# Workflow Diagram Maintenance
+
+## Regenerating SVG from Excalidraw
+
+When you edit `workflow-method-greenfield.excalidraw`, regenerate the SVG:
+
+1. Open https://excalidraw.com/
+2. Load the `.excalidraw` file
+3. Click menu (☰) → Export image → SVG
+4. **Set "Scale" to 1x** (default is 2x)
+5. Click "Export"
+6. Save as `workflow-method-greenfield.svg`
+7. **Validate the changes** (see below)
+8. Commit both files together
+
+**Important:**
+
+- Always use **1x scale** to maintain consistent dimensions
+- Automated export tools (`excalidraw-to-svg`) are broken - use manual export only
+
+## Visual Validation
+
+After regenerating the SVG, validate that it renders correctly:
+
+```bash
+./tools/validate-svg-changes.sh src/modules/bmm/docs/images/workflow-method-greenfield.svg
+```
+
+This script:
+
+- Checks for required dependencies (Playwright, ImageMagick)
+- Installs Playwright locally if needed (no package.json pollution)
+- Renders old vs new SVG using browser-accurate rendering
+- Compares pixel-by-pixel and generates a diff image
+- Outputs a prompt for AI visual analysis (paste into Gemini/Claude)
+
+**Threshold**: <0.01% difference is acceptable (anti-aliasing variations)