fix: skip tree-sitter error strings in folded file context

- Add isTreeSitterErrorString helper to detect error messages
- Skip files that return error strings instead of embedding them
- Add test for error string handling

Author: roomote

src/core/condense/__tests__/foldedFileContext.spec.ts

@@ -94,6 +94,32 @@ describe("foldedFileContext", () => {
 			expect(result.filesSkipped).toBe(1)
 		})
 
+		it("should skip files when parseSourceCodeDefinitions returns error strings", async () => {
+			// Tree-sitter can return error strings for missing or denied files
+			// These should be treated as skipped, not embedded in the output
+			mockedParseSourceCodeDefinitions
+				.mockResolvedValueOnce("1--3 | export const x = 1")
+				.mockResolvedValueOnce("This file does not exist or you do not have permission to access it.")
+				.mockResolvedValueOnce("Unsupported file type: /test/file.xyz")
+
+			const result = await generateFoldedFileContext(["/test/valid.ts", "/test/missing.ts", "/test/file.xyz"], {
+				cwd: "/test",
+			})
+
+			// Only the first file should be processed, the other two return error strings
+			expect(result.filesProcessed).toBe(1)
+			expect(result.filesSkipped).toBe(2)
+
+			// The content should NOT contain the error messages
+			expect(result.content).not.toContain("does not exist")
+			expect(result.content).not.toContain("do not have permission")
+			expect(result.content).not.toContain("Unsupported file type")
+
+			// But it should contain the valid file's content
+			expect(result.content).toContain("## File Context: /test/valid.ts")
+			expect(result.content).toContain("export const x = 1")
+		})
+
 		it("should respect character budget limit", async () => {
 			// Create multiple files that would exceed a small budget
 			const longDefinitions = `1--3 | export function longFunctionName1()

src/core/condense/foldedFileContext.ts

@@ -2,6 +2,17 @@ import * as path from "path"
 import { parseSourceCodeDefinitionsForFile } from "../../services/tree-sitter"
 import { RooIgnoreController } from "../ignore/RooIgnoreController"
 
+/**
+ * Checks if a definitions string is actually an error message from tree-sitter
+ * rather than valid code definitions. These error strings should not be embedded
+ * in the folded file context - instead, the file should be skipped.
+ */
+function isTreeSitterErrorString(definitions: string): boolean {
+	// These are known error messages from parseSourceCodeDefinitionsForFile
+	const errorPatterns = ["This file does not exist", "do not have permission", "Unsupported file type:"]
+	return errorPatterns.some((pattern) => definitions.includes(pattern))
+}
+
 /**
  * Result of generating folded file context.
  */
@@ -91,8 +102,8 @@ export async function generateFoldedFileContext(
 			// Get the folded definitions using tree-sitter
 			const definitions = await parseSourceCodeDefinitionsForFile(absolutePath, rooIgnoreController)
 
-			if (!definitions) {
-				// File type not supported or no definitions found
+			if (!definitions || isTreeSitterErrorString(definitions)) {
+				// File type not supported, no definitions found, or error accessing file
 				result.filesSkipped++
 				continue
 			}