fix: trim dashes after truncation, not before

Bugbot correctly noted that .slice(0, 60) after dash-trim can
reintroduce a trailing dash. Reorder so trim runs after slice.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/core/src/__tests__/session-manager.test.ts

@@ -199,6 +199,20 @@ describe("spawn", () => {
     expect(session.branch!.replace("feat/", "").length).toBeLessThanOrEqual(60);
   });
 
+  it("does not leave trailing dash after truncation", async () => {
+    const sm = createSessionManager({ config, registry: mockRegistry });
+
+    // Craft input where the 60th char falls on a word boundary (dash)
+    const session = await sm.spawn({
+      projectId: "my-app",
+      issueId: "ab ".repeat(30), // "ab ab ab ..." → "ab-ab-ab-..." truncated at 60
+    });
+
+    const slug = session.branch!.replace("feat/", "");
+    expect(slug).not.toMatch(/-$/);
+    expect(slug).not.toMatch(/^-/);
+  });
+
   it("falls back to sessionId when issueId sanitizes to empty string", async () => {
     const sm = createSessionManager({ config, registry: mockRegistry });
 

packages/core/src/session-manager.ts

@@ -404,8 +404,8 @@ export function createSessionManager(deps: SessionManagerDeps): SessionManager {
         : id
             .toLowerCase()
             .replace(/[^a-z0-9]+/g, "-")
-            .replace(/^-+|-+$/g, "")
-            .slice(0, 60);
+            .slice(0, 60)
+            .replace(/^-+|-+$/g, "");
       branch = `feat/${slug || sessionId}`;
     } else {
       branch = `session/${sessionId}`;