docs: render architecture & flow diagrams as draw.io charts

Replace ASCII-art diagrams across the README and docs/ with editable
.drawio sources plus exported PNGs, so the diagrams render clearly in
rendered markdown and can be maintained/regenerated instead of being
hand-edited as fragile text art. Non-diagram blocks (code, folder
trees, UI wireframes) were left as text.

docs/plans/generate_plans.md

@@ -547,27 +547,8 @@ This section governs how implementation plans are executed. The goal is autonomo
 
 For each work package, follow this sequence:
 
-```
-┌─────────────────────────────────────────────────────┐
-│ 1. READ the WP description and acceptance criteria  │
-│ 2. READ all traced requirements (HLR bullets, KDD,  │
-│    CD constraints) to understand intent              │
-│ 3. IMPLEMENT the WP                                  │
-│    - Write code                                      │
-│    - Write unit tests for acceptance criteria         │
-│    - Write negative tests for prohibition criteria    │
-│ 4. VERIFY acceptance criteria                        │
-│    - Run tests: all must pass                        │
-│    - Walk each acceptance criterion line by line      │
-│    - If a criterion cannot be verified yet (depends   │
-│      on a later WP), note it as "deferred to WP-N"  │
-│ 5. UPDATE the phase execution checklist              │
-│    - Mark WP as complete with date                   │
-│    - Note any deferred criteria                      │
-│    - Note any questions logged                       │
-│ 6. COMMIT with message: "Phase N WP-M: <summary>"   │
-└─────────────────────────────────────────────────────┘
-```
+![generate-plans-per-work-package](diagrams/generate-plans-per-work-package.png)
+<!-- source: diagrams/generate-plans-per-work-package.drawio — edit, then re-export with export-drawio.sh -->
 
 ### Mid-Phase Compliance Check