fix: 回应独立 CR 的 P2/P3 意见（0×P1）

- P2-1 onOpen 收到真正落地的 tab：url 新建场景从 landed 态按 id 反查
  （补丁后对象），回调不再拿到未打 url 的 tab
- P2-2 插件设置行显式取值源：FeatureSettingsRows 新增 valueSource prop，
  插件行读自己的 pluginSettings blob——插件键与宿主 pref 同名时不再
  静默读宿主值（原投影合并有读宿主写插件的读写不对称）；prop 命名避开
  Object.prototype.valueOf 冲突
- P2-3 consumer 类型检查接入工程：package.json 新增 check:consumer-types
  脚本 + CI 在 build 后执行；脚本补 lib/types 存在性前置检查（防假绿）
- P3-1 url seed 只在新建时应用：dedupe 聚焦的 tab 不再被覆写 path
- P3-2 closeTab/activateTab 未知 id 严格 no-op：store.reduce 对同引用
  结果短路（不 notify、不重写 localStorage），根因修复 + 回归测试
- P3-3 closeTab/activateTab 增加可选 scope（cwd 随回调传递），Sidebar
  双树激活/关闭路径传入 { sessionId, cwd }
- P3-4 定向打开不再自动展开不可见 session 的面板
- P3-5 Sidebar 终端 pty 释放查找覆盖双树（底部面板终端不再漏掉 HTTP
  兜底）
- P3-6/P3-7 与 Nits：AGENTS.md/指南文档化（dedupeKey 纯函数、meta 用
  null 清除、回调 scope 的 cwd 语义）；consumer fixture 补常量导出覆盖

测试 +6（url 落地保真 / url 不覆写聚焦 / 未知 id 无 notify / 定向打开
不展开 / scope 随回调 / valueSource 键隔离），464 全绿；typecheck、
build、consumer 校验全部通过。

src/client/Sidebar.tsx

@@ -553,11 +553,17 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
       // TerminalView on unmount), and the agent-pty.close HTTP route is the
       // fallback when the WS is down.
       const current = store.getSnapshot().state
-      const leaf = current === undefined ? undefined : leafWithTab(current.splits, tabId)
+      // Terminal tabs may live in EITHER tree (the bottom panel hosts them
+      // too) — the pty-release lookup covers both, or the HTTP fallback is
+      // skipped for a bottom-panel terminal whose WS frame never arrived.
+      const leaf = current === undefined
+        ? undefined
+        : leafWithTab(current.splits, tabId) ?? leafWithTab(current.bottomSplits, tabId)
       const tab = leaf?.tabs.find(candidate => candidate.id === tabId)
       // Route through the service: the tab-bar close is the canonical close
-      // path (finds the pane itself, fires descriptor.onClose).
-      ctx.betterSidebar?.closeTab(tabId)
+      // path (finds the pane itself, fires descriptor.onClose); the session
+      // scope (with its cwd) rides to the callback.
+      ctx.betterSidebar?.closeTab(tabId, sessionId === undefined ? undefined : { sessionId, cwd })
       if (tab?.type === 'terminal') {
         if (isAgentTabId(tabId)) {
           const uuid = agentUuidOf(tabId)
@@ -569,8 +575,9 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
     },
     activateTab: (paneId, tabId) => {
       // Route through the service: same reducer (finds the pane in EITHER
-      // tree, sets the active pane) and fires descriptor.onActivate.
-      ctx.betterSidebar?.activateTab(tabId)
+      // tree, sets the active pane) and fires descriptor.onActivate; the
+      // session scope (with its cwd) rides to the callback.
+      ctx.betterSidebar?.activateTab(tabId, sessionId === undefined ? undefined : { sessionId, cwd })
     },
     focusPane: (paneId) => { store.reduce(s => ({ ...s, activePane: paneId })) },
     moveTabToEdge: (payload: TabDragPayload, toPane: string, zone: DropZone) => {