FN-6300: add live task chat tab

Add a live chat-style task detail tab for following and steering active agent work.

- Add TaskChatTab with grouped agent log bubbles, live-follow scrolling, and steering message composer.
- Share chat input autosize helpers between ChatView and task chat.
- Wire the Chat tab into task detail navigation with localized labels and regression coverage.

Files changed:
 docs/dashboard-guide.md                            |   2 +
 .../dashboard/app/components/AgentLogViewer.tsx    |   2 +-
 packages/dashboard/app/components/ChatView.tsx     |  25 +-
 packages/dashboard/app/components/TaskChatTab.css  | 193 ++++++++++++++
 packages/dashboard/app/components/TaskChatTab.tsx  | 276 +++++++++++++++++++++
 .../dashboard/app/components/TaskDetailModal.tsx   |  13 +-
 .../app/components/__tests__/TaskChatTab.test.tsx  | 181 ++++++++++++++
 .../TaskDetailModal.attachments-and-tabs.test.tsx  |  19 +-
 .../TaskDetailModal.definition-actions.test.tsx    | 104 ++++----
 ...etailModal.responsive-and-dependencies.test.tsx |   2 +-
 packages/dashboard/app/utils/chatInputAutosize.ts  |  18 ++
 packages/i18n/locales/en/app.json                  |   1 +
 packages/i18n/locales/es/app.json                  |   1 +
 packages/i18n/locales/fr/app.json                  |   1 +
 packages/i18n/locales/ko/app.json                  |   1 +
 packages/i18n/locales/zh-CN/app.json               |   1 +
 packages/i18n/locales/zh-TW/app.json               |   1 +
 17 files changed, 757 insertions(+), 84 deletions(-)

Fusion-Task-Id: FN-6300
Fusion-Task-Lineage: 1eb8a17b-3ca5-4cba-81c6-ac7ccce0a113

docs/dashboard-guide.md

@@ -728,6 +728,8 @@ Recommended workflow: ordinary chains stay as `Blocks N` so noise stays low, hig
 
 ### Logs → Agent Log view
 
+The **Chat** tab sits between Definition and Logs and presents a live, chat-styled transcript of task agent output. Consecutive entries are grouped by role and labeled as Planner, Executor, Reviewer, or Merger; legacy log rows without an agent role use the neutral Agent fallback. The transcript follows new live output when you are already near the bottom, but it preserves your scroll position when you review older messages. For active `in-progress` tasks with an assigned agent session, the composer sends guidance to the running agent through the same steering path used by comments; when no active session is available, the composer is disabled with an explanatory hint.
+
 The **Logs** tab includes an **Agent Log** subview designed for debugging long-running and tool-heavy sessions:
 
 - Full `thinking`, `tool_result`, and `tool_error` payloads are shown without entry-content truncation.