docs: convert standard diagrams from draw.io PNGs to inline Mermaid

Gitea renders mermaid inline, so the flow/state/hierarchy/DAG diagrams
move to text-in-markdown: auto-layout (removes the manual overlap-prone
draw.io step), diffable source, no committed binaries, and a dark-text
theme so labels stay legible. Keep draw.io PNGs only for the two complex
bespoke diagrams (logical architecture, env2 topology) where pixel
control still wins. All 24 mermaid blocks validated by rendering.

docs/plans/generate_plans.md

@@ -547,8 +547,27 @@ This section governs how implementation plans are executed. The goal is autonomo
 
 For each work package, follow this sequence:
 
-![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 -->
+```mermaid
+%%{init: {'theme':'base', 'themeVariables': {'textColor':'#111111','lineColor':'#555555','edgeLabelBackground':'#ffffff','fontSize':'15px'}}}%%
+flowchart TD
+    S1["1. READ the WP description and acceptance criteria"]
+    S2["2. READ all traced requirements (HLR bullets, KDD, CD constraints) to understand intent"]
+    S3["3. IMPLEMENT the WP<br/>• Write code<br/>• Write unit tests for acceptance criteria<br/>• Write negative tests for prohibition criteria"]
+    S4["4. VERIFY acceptance criteria<br/>• Run tests: all must pass<br/>• Walk each acceptance criterion line by line<br/>• If a criterion cannot be verified yet (depends on a later WP), note it as deferred to WP-N"]
+    S5["5. UPDATE the phase execution checklist<br/>• Mark WP as complete with date<br/>• Note any deferred criteria<br/>• Note any questions logged"]
+    S6["6. COMMIT with message:<br/>Phase N WP-M: summary"]
+
+    S1 --> S2 --> S3 --> S4 --> S5 --> S6
+
+    classDef start fill:#d5e8d4,stroke:#82b366,color:#111111;
+    classDef proc fill:#dae8fc,stroke:#6c8ebf,color:#111111;
+    classDef dec fill:#fff2cc,stroke:#d6b656,color:#111111;
+    classDef warn fill:#ffe6cc,stroke:#d79b00,color:#111111;
+    class S1,S2 proc
+    class S3 start
+    class S4,S5 dec
+    class S6 warn
+```
 
 ### Mid-Phase Compliance Check