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/notebook.ts

@@ -13,14 +13,16 @@ import { formatCount, formatErrorMessage, PREVIEW_LIMITS } from "./render-utils"
 
 const notebookSchema = Type.Object({
 	action: StringEnum(["edit", "insert", "delete"], {
-		description: "Action to perform on the notebook cell",
+		description: "cell action",
+		examples: ["edit", "insert", "delete"],
 	}),
-	notebook_path: Type.String({ description: "Path to the .ipynb file" }),
-	cell_index: Type.Number({ description: "0-based index of the cell to operate on" }),
-	content: Type.Optional(Type.String({ description: "New cell content (required for edit/insert)" })),
+	notebook_path: Type.String({ description: "notebook path", examples: ["analysis.ipynb"] }),
+	cell_index: Type.Number({ description: "cell index", examples: [0, 1] }),
+	content: Type.Optional(Type.String({ description: "new cell content" })),
 	cell_type: Type.Optional(
 		StringEnum(["code", "markdown"], {
-			description: "Cell type for insert (default: code)",
+			description: "cell type",
+			examples: ["code", "markdown"],
 		}),
 	),
 });