FN-7312: send task context to planner chat

Send bounded task state into task-detail planner chat so status and progress questions can be answered in context.

- Build reusable server-side planner chat context from task metadata, dependencies, steps, comments, activity, source, and review state.
- Pass and validate the task id on planner chat sends to keep sessions scoped to the current task.
- Update planner chat copy, docs, tests, and changeset coverage for task-aware status/progress questions.

Files changed:
 .changeset/fn-7312-task-planner-chat-context.md    |   7 +
 docs/dashboard-guide.md                            |   4 +-
 packages/dashboard/app/api/legacy.ts               |   5 +-
 .../app/components/TaskPlannerChatTab.tsx          |   5 +-
 .../__tests__/TaskPlannerChatTab.test.tsx          |  22 ++
 .../dashboard/src/__tests__/chat-manager.test.ts   |  17 +-
 .../dashboard/src/__tests__/chat-routes.test.ts    |  76 +++++
 .../__tests__/task-planner-chat-context.test.ts    | 165 +++++++++++
 packages/dashboard/src/chat.ts                     |  92 +-----
 .../dashboard/src/routes/register-chat-routes.ts   |  11 +-
 .../dashboard/src/task-planner-chat-context.ts     | 326 +++++++++++++++++++++
 11 files changed, 634 insertions(+), 96 deletions(-)

Fusion-Task-Id: FN-7312

Fusion-Task-Lineage: 90cf0fe3-3984-4a67-bb44-fce492c256eb

Co-authored-by: Fusion (runfusion.ai) <noreply@runfusion.ai>

packages/dashboard/app/api/legacy.ts

@@ -10241,7 +10241,7 @@ export function streamChatResponse(
   handlers: ChatStreamHandlers,
   attachments?: File[],
   projectId?: string,
-  options?: { maxReconnectAttempts?: number; firstEventTimeoutMs?: number },
+  options?: { maxReconnectAttempts?: number; firstEventTimeoutMs?: number; taskId?: string },
 ): { close: () => void; isConnected: () => boolean } {
   const url = buildApiUrl(withProjectId(`/chat/sessions/${encodeURIComponent(sessionId)}/messages`, projectId));
 
@@ -10337,10 +10337,11 @@ export function streamChatResponse(
         ? (() => {
             const formData = new FormData();
             formData.append("content", content);
+            if (options?.taskId) formData.append("taskId", options.taskId);
             attachments.forEach((file) => formData.append("attachments", file));
             return formData;
           })()
-        : JSON.stringify({ content });
+        : JSON.stringify({ content, ...(options?.taskId ? { taskId: options.taskId } : {}) });
 
       const res = await fetch(url, {
         method: "POST",