improve(ui): simplify Sessions visual hierarchy (#127793)

* style(ui): simplify Sessions visual hierarchy

* test(ui): cover compact Sessions facts responsively

* style(ui): tighten Sessions vertical rhythm

* style(ui): simplify Sessions filters

* style(ui): align Sessions filter trigger

* test(ui): advertise transcript search in current mocks

Co-authored-by: Tak Hoffman <781889+Takhoffman@users.noreply.github.com>

---------

Co-authored-by: RoboClaw <309084314+roboclaw-bot@users.noreply.github.com>
Co-authored-by: Tak Hoffman <781889+Takhoffman@users.noreply.github.com>

scripts/control-ui-mock-dev.ts

@@ -1750,6 +1750,7 @@ async function createChatPickerScenario(
       "sessions.groups.rename",
       "sessions.patch",
       "sessions.patchMany",
+      "sessions.search",
       "sessions.catalog.list",
       "sessions.catalog.read",
       "sessions.create",
@@ -2652,6 +2653,7 @@ async function createChatPickerScenario(
           ...buildSessionListCases([...sessions, ...archivedSessions], {}, MOCK_SESSION_OWNERS),
         ],
       },
+      "sessions.search": { results: [] },
       ...(fixture === "workboard" ? workboardMocks.methodResponses : {}),
     },
     models: modelProviders.models,