fix(coding-agent): handled xdev execution errors with mounted tool renderer

- Catch execution errors in XdevRegistry and render them using the mounted tool's error handling.
- Preserve xdev dispatch context when device execution fails.

packages/coding-agent/test/write-xdev-dispatch.test.ts

@@ -6,9 +6,12 @@ import { Settings } from "@oh-my-pi/pi-coding-agent/config/settings";
 import * as themeModule from "@oh-my-pi/pi-coding-agent/modes/theme/theme";
 import { ToolChoiceQueue } from "@oh-my-pi/pi-coding-agent/session/tool-choice-queue";
 import { createTools, type ToolSession } from "@oh-my-pi/pi-coding-agent/tools";
-import { writeToolRenderer } from "@oh-my-pi/pi-coding-agent/tools/write";
+import { githubToolRenderer } from "@oh-my-pi/pi-coding-agent/tools/gh-renderer";
+import { ToolError } from "@oh-my-pi/pi-coding-agent/tools/tool-errors";
+import { WriteTool, writeToolRenderer } from "@oh-my-pi/pi-coding-agent/tools/write";
 import { XdevRegistry } from "@oh-my-pi/pi-coding-agent/tools/xdev";
 import { removeWithRetries } from "@oh-my-pi/pi-utils";
+import { type } from "arktype";
 
 // xdev mounting is default-on: discoverable tools like ast_edit unmount into
 // xd://, and a plain `write xd://ast_edit` dispatches them. These guard the
@@ -182,6 +185,49 @@ describe("read and write route xd:// device URLs", () => {
 		expect(rendered).toBeDefined();
 	});
 
+	it("renders device execution errors as the mounted tool instead of write", async () => {
+		await themeModule.initTheme();
+		const uiTheme = (await themeModule.getThemeByName("dark")) ?? (await themeModule.getThemeByName("light"));
+		if (!uiTheme) throw new Error("expected an initialized theme");
+
+		const githubDevice = {
+			name: "github",
+			label: "GitHub",
+			description: "fixture",
+			parameters: type({ op: "string" }),
+			...githubToolRenderer,
+			async execute() {
+				throw new ToolError("gh: Not Found (HTTP 404)");
+			},
+		};
+		const registry = new XdevRegistry([githubDevice]);
+		const write = new WriteTool(xdevSession(process.cwd(), { xdevRegistry: registry }));
+		const content = JSON.stringify({ op: "repo_view" });
+
+		const result = await write.execute("write-xdev-error", { path: "xd://github", content });
+		expect(result.isError).toBe(true);
+		expect(result.details?.xdev).toMatchObject({
+			tool: "github",
+			mode: "execute",
+			args: { op: "repo_view" },
+		});
+
+		const component = writeToolRenderer.renderResult(
+			result,
+			{
+				expanded: false,
+				isPartial: false,
+				renderContext: { resolveXdevMounted: name => registry.get(name) },
+			},
+			uiTheme,
+			{ path: "xd://github", content },
+		);
+		const rendered = Bun.stripANSI(component.render(80).join("\n"));
+		expect(rendered).toContain("GitHub Repo");
+		expect(rendered).toContain("gh: Not Found (HTTP 404)");
+		expect(rendered).not.toContain("Write");
+	});
+
 	it("docsAll inlines small device docs and falls back to a listing past the caps", async () => {
 		const tempDir = await fs.mkdtemp(path.join(os.tmpdir(), "write-xdev-docs-"));
 		try {