feat: replace ASCII diagram with mermaid and enable mermaid fences

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jayhesselberth

docs/index.md

@@ -8,11 +8,10 @@ Launch [Positron](https://github.com/posit-dev/positron) on **Alpine** (CU Bould
 
 The script allocates a compute node on your HPC cluster via SLURM and provides SSH connection instructions for remote development with Positron. It uses a **ProxyJump** SSH pattern to connect through the login node to your allocated compute node.
 
-```
-┌──────────────┐       ┌──────────────┐       ┌──────────────┐
-│  Your Machine│──SSH──▶│  Login Node  │──SSH──▶│ Compute Node │
-│  (Positron)  │       │  (gateway)   │       │ (workspace)  │
-└──────────────┘       └──────────────┘       └──────────────┘
+```mermaid
+graph LR
+  A["🖥️ Your Machine\n(Positron)"] -->|SSH| B["🌐 Login Node\n(gateway)"]
+  B -->|ProxyJump| C["⚡ Compute Node\n(workspace)"]
 ```
 
 The workflow is three steps:

zensical.toml

@@ -44,6 +44,9 @@ toggle.name = "Switch to light mode"
 [project.markdown_extensions.pymdownx.details]
 
 [project.markdown_extensions.pymdownx.superfences]
+custom_fences = [
+  { name = "mermaid", class = "mermaid", format = "pymdownx.superfences.fence_code_format" }
+]
 
 [project.markdown_extensions.pymdownx.tabbed]
 alternate_style = true