test(web): shrink the assembled jsdom lane to one built-bundle boot smoke

The seven behavior-pinning snapshots (workspace-flow, slash-flow,
todo-display, session-title, session-actions, terminal-card,
code-mode-fixture) asserted per-package behavior through the whole
built app: every assertion now lives in the owning package's suite at
equal strength (SlotTestRuntime benches assemble the same plugin apply
over the production slot machinery), while the assembled layer kept
re-failing on unrelated churn at 10s-timeout debugging cost.

What only this lane can prove is the artifact plane: lib/client.js
bundles loading through the ModuleLoader path, staged boot activation
across the inject layers, per-plugin CSS injection, and a journey
reaching chat content over the fixture transport. built-boot.snapshot.ts
pins exactly that, and nothing else — behavior assertions belong to the
package suites.

apps/web/tests/snapshots/session-actions/rename-rows.json

@@ -1,14 +0,0 @@
-[
-  {
-    "label": "fixture4 sessions"
-  },
-  {
-    "label": "New Sessionnow"
-  },
-  {
-    "label": "分叉 实验记录now"
-  },
-  {
-    "label": "fixture2min"
-  }
-]

apps/web/tests/snapshots/session-title.json

@@ -1,12 +0,0 @@
-{
-  "initial": {
-    "sidebar": "Fixture 历史会话",
-    "breadcrumb": "Fixture 历史会话",
-    "documentTitle": "Fixture 历史会话 — DeepSeek Harness"
-  },
-  "revised": {
-    "sidebar": "Fixture 修订标题",
-    "breadcrumb": "Fixture 修订标题",
-    "documentTitle": "Fixture 修订标题 — DeepSeek Harness"
-  }
-}