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/lib/message-editor-drafts.ts

@@ -0,0 +1,95 @@
+import type { UploadedEditorImage } from "./im-editor-image"
+
+export type MessageEditorDraft = {
+  html: string
+  revision: number
+  objectUrls: Set<string>
+  uploadedImages: Map<string, UploadedEditorImage & { url: string }>
+}
+
+type PendingDraftSend = {
+  key: string
+  draft: MessageEditorDraft
+  revision: number
+}
+
+/** In-memory only: neither messages nor temporary image URLs belong in storage. */
+export function createMessageEditorDraftStore() {
+  const drafts = new Map<string, MessageEditorDraft>()
+  let pendingSend: PendingDraftSend | null = null
+  let scope: string | undefined
+  const sendingListeners = new Set<() => void>()
+  const notifySending = () => { for (const listener of sendingListeners) listener() }
+  const listeners = new Set<(draft: MessageEditorDraft) => void>()
+  const notify = (draft: MessageEditorDraft) => { for (const listener of listeners) listener(draft) }
+
+  function release(draft: MessageEditorDraft) {
+    for (const url of draft.objectUrls) URL.revokeObjectURL(url)
+    draft.objectUrls.clear()
+    draft.uploadedImages.clear()
+  }
+
+  function clear() {
+    for (const draft of drafts.values()) release(draft)
+    drafts.clear()
+    pendingSend = null
+    notifySending()
+  }
+
+  return {
+    clear,
+    notify,
+    subscribe(listener: (draft: MessageEditorDraft) => void) {
+      listeners.add(listener)
+      return () => { listeners.delete(listener) }
+    },
+    isSending() { return pendingSend !== null },
+    subscribeSending(listener: () => void) {
+      sendingListeners.add(listener)
+      return () => { sendingListeners.delete(listener) }
+    },
+    setScope(nextScope: string) {
+      if (scope !== nextScope) {
+        clear()
+        scope = nextScope
+      }
+    },
+    get(key: string): MessageEditorDraft {
+      let draft = drafts.get(key)
+      if (!draft) {
+        draft = { html: "", revision: 0, objectUrls: new Set(), uploadedImages: new Map() }
+        drafts.set(key, draft)
+      }
+      return draft
+    },
+    contains(key: string, draft: MessageEditorDraft) {
+      return drafts.get(key) === draft
+    },
+    update(draft: MessageEditorDraft, html: string) {
+      draft.html = html
+      draft.revision += 1
+    },
+    beginSend(key: string): PendingDraftSend | null {
+      const draft = drafts.get(key)
+      if (!draft || pendingSend) return null
+      pendingSend = { key, draft, revision: draft.revision }
+      notifySending()
+      return pendingSend
+    },
+    finishSend(sent: PendingDraftSend, succeeded: boolean) {
+      if (pendingSend !== sent) return false
+      pendingSend = null
+      notifySending()
+      if (!succeeded || drafts.get(sent.key) !== sent.draft || sent.draft.revision !== sent.revision) {
+        return false
+      }
+      sent.draft.html = ""
+      sent.draft.revision += 1
+      release(sent.draft)
+      notify(sent.draft)
+      return true
+    },
+  }
+}
+
+export type MessageEditorDraftStore = ReturnType<typeof createMessageEditorDraftStore>