fix(annotate): support @ markdown file references (#488)

OpenCode can pass annotate targets as @file references, so resolve markdown paths with an @ fallback only after the primary lookup misses. This preserves real @-prefixed filenames while making @README.md and quoted @ inputs resolve reliably.

packages/server/resolve-file.test.ts

@@ -106,6 +106,33 @@ describe("resolveMarkdownFile", () => {
     });
   });
 
+  test("resolves @ filename via fallback when @ file does not exist", async () => {
+    const root = createTempProject({ "README.md": "# Hello" });
+    const result = resolveMarkdownFile("@README.md", root);
+    expect(result).toEqual({
+      kind: "found",
+      path: resolve(root, "README.md"),
+    });
+  });
+
+  test("prioritizes real @ filename before fallback", async () => {
+    const root = createTempProject({ "@README.md": "# At" });
+    const result = resolveMarkdownFile("@README.md", root);
+    expect(result).toEqual({
+      kind: "found",
+      path: resolve(root, "@README.md"),
+    });
+  });
+
+  test("resolves quoted @ filename", async () => {
+    const root = createTempProject({ "README.md": "# Hello" });
+    const result = resolveMarkdownFile('"@README.md"', root);
+    expect(result).toEqual({
+      kind: "found",
+      path: resolve(root, "README.md"),
+    });
+  });
+
   test("resolves relative paths with Windows separators", async () => {
     const root = createTempProject({ "docs/test-plan.md": "# Test plan\n" });
     const result = resolveMarkdownFile("docs\\test-plan.md", root);
@@ -147,6 +174,19 @@ describe("resolveMarkdownFile", () => {
     }
   });
 
+  test("returns ambiguous in @ fallback when target exists multiple times", async () => {
+    const root = createTempProject({
+      "docs/plan.md": "# Plan 1",
+      "api/plan.md": "# Plan 2",
+    });
+    const result = resolveMarkdownFile("@plan.md", root);
+    expect(result.kind).toBe("ambiguous");
+    if (result.kind === "ambiguous") {
+      expect(result.input).toBe("@plan.md");
+      expect(result.matches).toHaveLength(2);
+    }
+  });
+
   // Ignored directories
 
   test("skips node_modules", async () => {
@@ -190,6 +230,12 @@ describe("resolveMarkdownFile", () => {
     expect(result.kind).toBe("not_found");
   });
 
+  test("returns not_found for @ path that cannot be resolved", async () => {
+    const root = createTempProject();
+    const result = resolveMarkdownFile("@nope.md", root);
+    expect(result).toEqual({ kind: "not_found", input: "@nope.md" });
+  });
+
   test("handles deeply nested files", async () => {
     const root = createTempProject({
       "a/b/c/d/deep.md": "# Deep",

packages/shared/resolve-file.ts

@@ -78,6 +78,20 @@ function isSearchableMarkdownPath(input: string): boolean {
 	return MARKDOWN_PATH_REGEX.test(input.trim());
 }
 
+function stripWrappingQuotes(input: string): string {
+	if (input.length < 2) {
+		return input;
+	}
+
+	const first = input[0];
+	const last = input[input.length - 1];
+	if ((first === '"' && last === '"') || (first === "'" && last === "'")) {
+		return input.slice(1, -1);
+	}
+
+	return input;
+}
+
 /** Check if a path looks like a Windows absolute path (e.g. C:\ or C:/) */
 function hasWindowsDriveLetter(input: string): boolean {
 	return /^[a-zA-Z]:[/\\]/.test(input);
@@ -155,12 +169,10 @@ export function isAbsoluteMarkdownPath(
  * @param input - User-provided path (absolute, relative, or bare filename)
  * @param projectRoot - Project root directory to search within
  */
-export function resolveMarkdownFile(
+function resolveMarkdownFileCore(
 	input: string,
 	projectRoot: string,
 ): ResolveResult {
-	// Trim whitespace/CR that may leak from Windows shell pipelines
-	input = input.trim();
 	const normalizedInput = normalizeMarkdownPathInput(input);
 	const searchInput = normalizeSeparators(normalizedInput);
 	const isBareFilename = !searchInput.includes("/");
@@ -218,6 +230,47 @@ export function resolveMarkdownFile(
 	return { kind: "not_found", input };
 }
 
+/**
+ * Resolve a markdown file path within a project root.
+ *
+ * @param input - User-provided path (absolute, relative, or bare filename)
+ * @param projectRoot - Project root directory to search within
+ */
+export function resolveMarkdownFile(
+	input: string,
+	projectRoot: string,
+): ResolveResult {
+	const originalInput = input.trim();
+	const unquotedInput = stripWrappingQuotes(originalInput);
+
+	const primary = resolveMarkdownFileCore(unquotedInput, projectRoot);
+	if (primary.kind === "found") {
+		return primary;
+	}
+	if (primary.kind === "ambiguous") {
+		return { ...primary, input: originalInput };
+	}
+
+	if (!unquotedInput.startsWith("@")) {
+		return { kind: "not_found", input: originalInput };
+	}
+
+	const normalizedInput = unquotedInput.replace(/^@+/, "");
+	if (!normalizedInput) {
+		return { kind: "not_found", input: originalInput };
+	}
+
+	const fallback = resolveMarkdownFileCore(normalizedInput, projectRoot);
+	if (fallback.kind === "found") {
+		return fallback;
+	}
+	if (fallback.kind === "ambiguous") {
+		return { ...fallback, input: originalInput };
+	}
+
+	return { kind: "not_found", input: originalInput };
+}
+
 /**
  * Check if a directory contains at least one markdown file.
  * Used to validate folder annotation targets.