Generate diagram workflow

Author: fizyk

.github/workflows/diagram.yml

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+name: Render Mermaid Diagrams
+on:
+  push:
+    paths:
+      - 'docs/*.mmd' # Trigger only when mermaid files change
+
+jobs:
+  render:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install Mermaid CLI
+        run: npm install -g @mermaid-js/mermaid-cli
+
+      - name: Render Diagram
+        run: mmdc -i docs/architecture.mmd -o docs/images/architecture.svg -t neutral
+
+      - name: Commit and Push
+        run: |
+          git config --local user.email "action@github.com"
+          git config --local user.name "GitHub Action"
+          git add docs/images/architecture.svg
+          git commit -m "docs: update rendered mermaid diagram" || exit 0
+          git push

docs/architecture.mmd

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+sequenceDiagram
+    autonumber
+    participant Pytest as Pytest runner
+    participant ProcFactory as postgresql_proc_factory
+    participant PgServer as PostgreSQL process
+    participant TemplateDB as Template DB (seeded)
+    participant TestDB as Per-test DB (clone)
+
+    Pytest->>ProcFactory: request postgresql_proc with load=[load_database]
+    ProcFactory->>PgServer: start server
+    ProcFactory->>TemplateDB: invoke load_database (create metadata, seed data)
+    Note right of TemplateDB: Template is created and seeded once per full run
+    loop per test
+        Pytest->>PgServer: request clone of TemplateDB
+        PgServer->>TestDB: create cloned database for test
+        Pytest->>TestDB: run test using cloned DB
+        Pytest->>TestDB: teardown: commit transaction
+        Pytest->>TestDB: teardown: drop_all metadata (cleanup)
+    end