Replace ASCII diagrams with Mermaid, add missing SWDError to hierarchy

Use astro-mermaid (client-side) for 3 diagrams: DAP architecture in
swd-operations, exception hierarchy in error-handling and exceptions
reference. Also fixes stale error-handling.mdx that was missing SWDError
from the hierarchy diagram and import example.

astro.config.mjs

@@ -1,11 +1,13 @@
 import { defineConfig } from 'astro/config';
 import starlight from '@astrojs/starlight';
+import mermaid from 'astro-mermaid';
 
 export default defineConfig({
   site: 'https://openocd-python.warehack.ing',
   telemetry: false,
   devToolbar: { enabled: false },
   integrations: [
+    mermaid({ autoTheme: true }),
     starlight({
       title: 'openocd-python',
       description: 'Typed async-first Python bindings for OpenOCD',

package.json

@@ -10,10 +10,12 @@
     "astro": "astro"
   },
   "dependencies": {
-    "astro": "^5.17.2",
     "@astrojs/starlight": "^0.35.0",
-    "sharp": "^0.33.0",
+    "@iconify-json/lucide": "^1.2.0",
+    "astro": "^5.17.2",
     "astro-icon": "^1.1.0",
-    "@iconify-json/lucide": "^1.2.0"
+    "astro-mermaid": "^1.3.1",
+    "mermaid": "^11.12.3",
+    "sharp": "^0.33.0"
   }
 }

src/content/docs/guides/error-handling.mdx

@@ -9,17 +9,18 @@ openocd-python uses a structured exception hierarchy rooted at `OpenOCDError`. E
 
 ## Exception hierarchy
 
-```
-OpenOCDError
-├── ConnectionError        # TCP connection failures
-├── TimeoutError           # Deadline exceeded
-├── TargetError            # Target not responding or returned an error
-│   └── TargetNotHaltedError   # Operation requires halted target
-├── FlashError             # Flash operation failed
-├── JTAGError              # JTAG communication error
-├── SVDError               # SVD file or parsing error
-├── ProcessError           # OpenOCD subprocess failed
-└── BreakpointError        # Breakpoint/watchpoint operation failed
+```mermaid
+graph TD
+  OpenOCDError --> ConnectionError
+  OpenOCDError --> TimeoutError
+  OpenOCDError --> TargetError
+  TargetError --> TargetNotHaltedError
+  OpenOCDError --> FlashError
+  OpenOCDError --> JTAGError
+  OpenOCDError --> SWDError
+  OpenOCDError --> SVDError
+  OpenOCDError --> ProcessError
+  OpenOCDError --> BreakpointError
 ```
 
 All exceptions are importable from the top-level `openocd` package:
@@ -33,6 +34,7 @@ from openocd import (
     TargetNotHaltedError,
     FlashError,
     JTAGError,
+    SWDError,
     SVDError,
     ProcessError,
 )

src/content/docs/guides/swd-operations.mdx

@@ -37,15 +37,16 @@ Both transports share the higher-level subsystems (target, memory, registers, fl
 
 An ARM CoreSight debug system has a **Debug Port** (DP) connected to one or more **Access Ports** (APs):
 
-```
-┌─────────────┐
-│    DP        │  ← DPIDR, TARGETID, CTRL/STAT
-│  (SWDIO)    │
-├─────────────┤
-│ AP #0       │  ← MEM-AP (AHB/APB/AXI bus access)
-│ AP #1       │  ← JTAG-AP, additional MEM-AP, etc.
-│ ...         │
-└─────────────┘
+```mermaid
+graph TD
+  DP["<b>Debug Port (DP)</b><br/>DPIDR · TARGETID · CTRL/STAT"]
+  AP0["<b>AP #0</b> — MEM-AP<br/>AHB / APB / AXI bus access"]
+  AP1["<b>AP #1</b> — JTAG-AP<br/>Additional MEM-AP, etc."]
+  APn["..."]
+
+  DP --> AP0
+  DP --> AP1
+  DP --> APn
 ```
 
 - **DP registers** (address 0x0 - 0x24): Debug port identification and control

src/content/docs/reference/exceptions.mdx

@@ -25,18 +25,18 @@ from openocd.breakpoints import BreakpointError
 
 ## Hierarchy
 
-```
-OpenOCDError
-  +-- ConnectionError
-  +-- TimeoutError
-  +-- TargetError
-  |     +-- TargetNotHaltedError
-  +-- FlashError
-  +-- JTAGError
-  +-- SWDError
-  +-- SVDError
-  +-- ProcessError
-  +-- BreakpointError
+```mermaid
+graph TD
+  OpenOCDError --> ConnectionError
+  OpenOCDError --> TimeoutError
+  OpenOCDError --> TargetError
+  TargetError --> TargetNotHaltedError
+  OpenOCDError --> FlashError
+  OpenOCDError --> JTAGError
+  OpenOCDError --> SWDError
+  OpenOCDError --> SVDError
+  OpenOCDError --> ProcessError
+  OpenOCDError --> BreakpointError
 ```
 
 <Aside type="note">