docs(search): improve search_code query description to prevent 422 errors

The previous description gave AI models insufficient guidance on
GitHub code search syntax, leading to common mistakes like:
- Using \| instead of /...|.../ for regex OR
- Confusing filename: with path: qualifiers
- Misunderstanding boolean operator precedence

The new description explicitly documents:
- Qualifiers: repo:, org:, language:, path:, path:/regex/, symbol:, content:, is:
- Boolean operators: AND, OR, NOT, parentheses
- Regex syntax: surround with slashes e.g. /foo|bar/
- Glob patterns in path: path:*.ts, path:/src/**/*.js

Fixes #2390

Author: Will-hxw

pkg/github/search.go

@@ -173,7 +173,7 @@ func SearchCode(t translations.TranslationHelperFunc) inventory.ServerTool {
 		Properties: map[string]*jsonschema.Schema{
 			"query": {
 				Type:        "string",
-				Description: "Search query using GitHub's powerful code search syntax. Examples: 'content:Skill language:Java org:github', 'NOT is:archived language:Python OR language:go', 'repo:github/github-mcp-server'. Supports exact matching, language filters, path filters, and more.",
+				Description: "Search query using GitHub code search syntax. Qualifiers: repo:owner/repo, org:name, language:Go, path:src/*.js, path:/regex/, symbol:Name, content:term, is:archived|fork. Boolean: AND, OR, NOT, parentheses. Regex: surround with slashes e.g. /sparse.*index/. Glob in path: path:*.ts, path:/src/**/*.js. Examples: 'MyFunc language:go repo:owner/repo', 'symbol:WithContext language:go', '/GetAttributes|SetAttributes/ repo:owner/repo', '(Foo OR Bar) path:src repo:owner/repo'.",
 			},
 			"sort": {
 				Type:        "string",