feat(ast-grep): rewrite tool descriptions to prevent regex-style misuse

The previous description (41 words) told the LLM to write 'complete AST
nodes' but did not explain that regex syntax is the #1 failure mode. It
also shipped a bug: the Python example 'def $FUNC($$$):' had a trailing
colon that the hint system actively flags as wrong.

Extract descriptions into tool-descriptions.ts and rewrite:
- Open with 'This is NOT regex' so the constraint is unmissable
- List the four regex patterns that do not work (|, .*, \\w, [a-z])
  with the corrective action for each
- Tell the LLM to switch to grep when the pattern is text-shaped
- Fix the Python example (no trailing colon) and add Go and Rust rows
  since the failing reports came from Go codebases
- Shorten the pattern-param description with the same anti-regex list

Also harden the LSP reference for the new test files using the
bun-types triple-slash directive already used elsewhere.

src/tools/ast-grep/tools.ts

@@ -4,6 +4,11 @@ import { CLI_LANGUAGES } from "./constants"
 import { runSg } from "./cli"
 import { formatSearchResult, formatReplaceResult } from "./result-formatter"
 import { getPatternHint } from "./pattern-hints"
+import {
+  AST_GREP_REPLACE_DESCRIPTION,
+  AST_GREP_SEARCH_DESCRIPTION,
+  AST_GREP_SEARCH_PATTERN_PARAM,
+} from "./tool-descriptions"
 import type { CliLanguage } from "./types"
 
 async function showOutputToUser(context: unknown, output: string): Promise<void> {
@@ -15,14 +20,9 @@ async function showOutputToUser(context: unknown, output: string): Promise<void>
 
 export function createAstGrepTools(ctx: PluginInput): Record<string, ToolDefinition> {
   const ast_grep_search: ToolDefinition = tool({
-    description:
-      "Search code patterns across filesystem using AST-aware matching. Supports 25 languages. " +
-      "Use meta-variables: $VAR (single node), $$$ (multiple nodes). " +
-      "IMPORTANT: Patterns must be complete AST nodes (valid code). " +
-      "For functions, include params and body: 'export async function $NAME($$$) { $$$ }' not 'export async function $NAME'. " +
-      "Examples: 'console.log($MSG)', 'def $FUNC($$$):', 'async function $NAME($$$)'",
+    description: AST_GREP_SEARCH_DESCRIPTION,
     args: {
-      pattern: tool.schema.string().describe("AST pattern with meta-variables ($VAR, $$$). Must be complete AST node."),
+      pattern: tool.schema.string().describe(AST_GREP_SEARCH_PATTERN_PARAM),
       lang: tool.schema.enum(CLI_LANGUAGES).describe("Target language"),
       paths: tool.schema.array(tool.schema.string()).optional().describe("Paths to search (default: ['.'])"),
       globs: tool.schema.array(tool.schema.string()).optional().describe("Include/exclude globs (prefix ! to exclude)"),
@@ -58,10 +58,7 @@ export function createAstGrepTools(ctx: PluginInput): Record<string, ToolDefinit
   })
 
   const ast_grep_replace: ToolDefinition = tool({
-    description:
-      "Replace code patterns across filesystem with AST-aware rewriting. " +
-      "Dry-run by default. Use meta-variables in rewrite to preserve matched content. " +
-      "Example: pattern='console.log($MSG)' rewrite='logger.info($MSG)'",
+    description: AST_GREP_REPLACE_DESCRIPTION,
     args: {
       pattern: tool.schema.string().describe("AST pattern to match"),
       rewrite: tool.schema.string().describe("Replacement pattern (can use $VAR from pattern)"),