fix(docs): enable JSON syntax highlighting for code blocks

The code blocks in Configuration.md used `jsonc` language identifier,
which is not supported by highlight.js by default. This caused JSON
code blocks to appear without syntax highlighting on the rendered site.

Fixed by:
- Loading JSON language module in highlight.js initialization
- Changing `jsonc` to `json` in all code blocks (JSON supports comments)

The `json` language properly highlights both standard JSON and JSON
with comments (JSONC format), making it the correct choice for our
configuration examples.

Author: lambdalisue

docs/configuration.md

@@ -20,7 +20,7 @@ The first file found is used. JSONC files support `//` and `/* */` comments.
 
 ### Configuration Options
 
-```jsonc
+```json
 {
   // Glob patterns for scenario file discovery
   "includes": ["probitas/**/*.probitas.ts"],
@@ -72,7 +72,7 @@ Controls when the test runner stops execution:
 - `1`: Fail-fast mode - stop immediately on first failure
 - `n`: Stop after n failures
 
-```jsonc
+```json
 {
   // Fail-fast: stop on first failure
   "maxFailures": 1
@@ -84,7 +84,7 @@ Controls when the test runner stops execution:
 Set default timeout and retry behavior for all steps across all scenarios. These
 defaults can be overridden at the scenario level or individual step level.
 
-```jsonc
+```json
 {
   "stepOptions": {
     // Default timeout for each step in milliseconds

templates/scripts.ts

@@ -33,6 +33,7 @@ async function ensureHljs() {
   if (window.hljs) return;
   await loadScript(\`\${HLJS_CDN}/highlight.min.js\`);
   await loadScript(\`\${HLJS_CDN}/languages/typescript.min.js\`);
+  await loadScript(\`\${HLJS_CDN}/languages/json.min.js\`);
 }
 
 function updateHljsTheme(theme) {