feat(coding-agent/tools): added examples to coding-agent tools

- Added `examples` support to `StringEnum` schemas and propagated it to tool metadata.
- Added concise descriptions and example values across coding-agent tool schemas for clearer guidance.
- Documented the new StringEnum examples capability in `packages/ai/CHANGELOG.md`.
- Cast `real` to `HASHLINE_BIGRAMS` elements in `staleBigramFor` test setup.

packages/coding-agent/src/tools/write.ts

@@ -44,8 +44,8 @@ import { ToolError } from "./tool-errors";
 import { toolResult } from "./tool-result";
 
 const writeSchema = Type.Object({
-	path: Type.String({ description: "Path to the file to write" }),
-	content: Type.String({ description: "Content to write to the file" }),
+	path: Type.String({ description: "file path", examples: ["src/new.ts"] }),
+	content: Type.String({ description: "file content" }),
 });
 
 export type WriteToolInput = Static<typeof writeSchema>;