fix(coding-agent): browser default, patch error path, mcp:// selectors, find timeout/sort, DAP launch races, debugpy diagnostics

- browser tool's existing-tab re-nav defaults to waitUntil: 'load' (matching
  new-tab path); identical acquireTab() calls no longer hang on dev servers
- patch tool error path uses caller-supplied relative path; absolute
  resolvedPath stays in structured context only ($HOME no longer leaks to TUI)
- splitInternalUrlSel keeps mcp:// resource URIs opaque even when they end in
  ':raw' or '/:1-50' (McpProtocolHandler matches by verbatim URI)
- find tool: timeout signal honored by onMatch; partial results sorted by
  mtime desc; backslash-escaped commas skipped in path-list validation
- DAP throwPreferredDapStartError waits up to 50ms for the underlying
  launch/attach error instead of one microtask
- debug tool surfaces 'python missing' and 'pip install debugpy' diagnostics
  separately when adapter: 'debugpy' is requested

packages/coding-agent/test/debug/dap-launch-failures.test.ts

@@ -182,6 +182,22 @@ describe("DAP launch failure handling", () => {
 			process.off("unhandledRejection", onUnhandled);
 		}
 	});
+
+	it("surfaces the adapter name and ENOENT when spawn fails", async () => {
+		const manager = new DapSessionManager();
+		spyOn(DapClient, "spawn").mockRejectedValue(new Error("ENOENT: no such file or directory, spawn 'lldb-dap'"));
+
+		let message = "";
+		try {
+			await manager.launch({ adapter: TEST_ADAPTER, program: "/bin/echo", cwd: process.cwd() });
+		} catch (error) {
+			expect(error).toBeInstanceOf(Error);
+			message = (error as Error).message;
+		}
+
+		expect(message).toContain("ENOENT");
+		expect(message).toContain(TEST_ADAPTER.name);
+	});
 });
 
 describe("DebugTool launch validation", () => {