feat: harden support, localize knowledge and add operator availability [skip ci]

Source-only publication of reviewed commit 64e96a7f423673dc29ad56485be9fc79bce8af1c.

Passed in isolation: focused frontend/backend tests, race checks, TypeScript typecheck, lint, Go compilation, Flowgram build, and deterministic SDK build/tests.

Not accepted as a production release: Next.js export/native assembly remains blocked by environment memory limits; browser interaction and MySQL staging acceptance remain unverified. No production server, database/schema, runtime configuration, deployment, release tag, or workflow execution was performed.

Expected source tree: 0a4a7528e9.

web/components/support-chat/close-navigation.ts

@@ -1,5 +1,16 @@
+// Modified in the independent hardening fork; see docs/hardening/README.md.
 export const SUPPORT_CHAT_CLOSED_PATH = "/support/chat/closed"
 
-export function getStandaloneClosedUrl() {
-  return SUPPORT_CHAT_CLOSED_PATH
+// Keep the entry context when dismissing/returning. These are always local
+// paths, never a caller-supplied redirect destination.
+function querySuffix(search: string) {
+  return search ? `?${new URLSearchParams(search).toString()}` : ""
+}
+
+export function getStandaloneClosedUrl(search = "") {
+  return `${SUPPORT_CHAT_CLOSED_PATH}${querySuffix(search)}`
+}
+
+export function getStandaloneChatUrl(search = "") {
+  return `/support/chat${querySuffix(search)}`
 }