docs(FN-823): clarify agent log content is never truncated per-entry

- Clarify in dashboard README that agent log entries are never truncated
- Add maxLength safeguards in store (getAgentLog), routes, useAgentLogs, and useMultiAgentLogs hooks
- Add tests for store, AgentLogViewer component, useAgentLogs hook, useMultiAgentLogs hook, and dashboard routes
- All tests verify that log text and detail fields are preserved in full without per-entry truncation

packages/dashboard/src/routes.test.ts

@@ -1603,6 +1603,25 @@ describe("Attachment routes", () => {
     expect(res.status).toBe(500);
     expect(res.body.error).toBe("disk error");
   });
+
+  it("GET /tasks/:id/logs — preserves long text and detail without truncation", async () => {
+    const longText = "A".repeat(5000);
+    const longDetail = "B".repeat(5000);
+    const fakeLogs = [
+      { timestamp: "2026-01-01T00:00:00Z", taskId: "KB-001", text: longText, type: "text" },
+      { timestamp: "2026-01-01T00:00:01Z", taskId: "KB-001", text: "Read", type: "tool", detail: longDetail },
+    ];
+    (store.getAgentLogs as ReturnType<typeof vi.fn>).mockResolvedValue(fakeLogs);
+
+    const res = await GET(buildApp(), "/api/tasks/KB-001/logs");
+
+    expect(res.status).toBe(200);
+    expect(res.body).toHaveLength(2);
+    expect(res.body[0].text).toBe(longText);
+    expect(res.body[0].text.length).toBe(5000);
+    expect(res.body[1].detail).toBe(longDetail);
+    expect(res.body[1].detail.length).toBe(5000);
+  });
 });
 
 // --- Models route tests ---

packages/dashboard/src/routes.ts

@@ -2042,7 +2042,9 @@ export function createApiRoutes(store: TaskStore, options?: ServerOptions): Rout
     }
   });
 
-  // Get historical agent logs for a task
+  // Get historical agent logs for a task.
+  // Per-entry text and detail fields are returned in full — no truncation.
+  // The 500-entry cap (MAX_LOG_ENTRIES) is a client-side whole-list limit.
   router.get("/tasks/:id/logs", async (req, res) => {
     try {
       const scopedStore = await getScopedStore(req);

packages/dashboard/src/server.ts

@@ -146,6 +146,10 @@ export function createServer(store: TaskStore, options?: ServerOptions): ReturnT
     // directly. Using getOrCreateProjectStore here would attach the listener
     // to a different EventEmitter instance that the executor never writes to,
     // breaking real-time log streaming.
+    //
+    // Per-entry text and detail fields are serialized in full — there is no
+    // SSE-level truncation.  The 500-entry cap is applied client-side in the
+    // React hooks (useAgentLogs / useMultiAgentLogs).
     const onAgentLog = (entry: { taskId: string; text: string; type: string; timestamp: string }) => {
       if (entry.taskId !== taskId) return;
       res.write(`event: agent:log\ndata: ${JSON.stringify(entry)}\n\n`);