steps 5-8: deep gut — purge chat/notes/projects/providers from code

main.go: remove ~300 lines of stale routes referencing deleted handlers
  (channels, messages, folders, personas, notes, projects, memories,
   models, providers, tasks, roles, usage, routing, capabilities, etc.)
  Fix branding: "Chat Switchboard" → "Switchboard Core"

pages: remove chat/notes/projects surface manifests and templates
  Keep: admin, settings, team-admin, workflow, workflow-landing

frontend: delete chat/, notes/, projects/ surface directories (19 files)
  Delete 5 CSS files (4,144 lines): sw-chat-*, sw-notes-*, sw-projects-*
  SDK: strip gutted API domains (594→287 lines), remove chatPane/notesPane

tests: remove integration_test.go (5,194 lines, broken imports to deleted
  packages) and perm_enforcement_test.go (551 lines, depended on deleted
  test helpers). Fix testmain_test.go (remove providers import).

openapi.yaml: replace 12,491-line stale spec with kernel auth stub.
  Full ICD rebuild is Step 8 proper.

Auth (builtin, mTLS, OIDC) untouched throughout.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/handlers/testmain_test.go

@@ -7,7 +7,6 @@ import (
 	"github.com/gin-gonic/gin"
 
 	"switchboard-core/database"
-	"switchboard-core/providers"
 
 	_ "modernc.org/sqlite" // register sqlite driver for DB_DRIVER=sqlite
 )
@@ -19,7 +18,6 @@ import (
 // Set DB_DRIVER=sqlite to run against SQLite instead of Postgres.
 func TestMain(m *testing.M) {
 	gin.SetMode(gin.TestMode)
-	providers.Init()
 
 	teardown := database.SetupTestDB()
 	code := m.Run()