feat(web): real chat list + P2P conversation view against live Tinode data

Phase 2 core loop: chat list and single-chat conversation now read/write real
Tinode topic data end to end, replacing the earlier hardcoded placeholders.

- lib/tinode/topics.ts: per-topic pub-sub layered on connection.ts's pattern
  (Topic.onData/onInfo/etc are single-slot callbacks, claimed once and fanned
  out). Implements the old app's subscribe lifecycle: `me` subscribed once
  per session (metadata only), each contact gets a one-shot preview
  subscription (withLaterData(1), never left), opening a conversation
  leaves-then-resubscribes with a full history page (withData, not
  withLaterData -- a preview prefetch already nudging _maxSeq would make
  withLaterData return empty).
- lib/tinode/hooks.ts: useChatList()/useTopicMessages() via
  useSyncExternalStore, snapshots cached and only invalidated on real
  topic-change notifications (not recomputed every render).
- lib/tinode/send.ts: sendText/retryMessage via createMessage+publishDraft
  (optimistic local echo), not the simpler publish() -- matches the old
  app's approach. retryMessage flushes the failed local entry and rebuilds
  before republishing, per the old app's context-menu retry handler.
- lib/messages/{time,avatar,attachments,status,preview,dispatch,drafty}:
  formatting utilities. Avatar color hash ports the old app's Java-style
  string hash but with modulus 11 (this design's palette) not the old app's
  16. @mention renders flat accent blue per the new design, not the old
  app's per-user hash color -- a deliberate simplification. File-type icons
  (PDF/Word/Excel/PPT) are new-design-only; the old app buckets all
  documents identically. Date/time formatting is written fresh against the
  design spec (today+time combined, weekday tier) since the old app never
  combines a relative-date word with a time in one string.
- ChatListColumn, MessageBubble, ConversationView: real components replacing
  the placeholder chat list and "占位" conversation view.
- tinode-sdk.d.ts: expanded with the real Topic/MetaGetBuilder/Drafty
  surface needed above, verified against the installed SDK source
  (createMessage/publishDraft/messages/msgStatus/noteRead/flushMessage/
  Drafty.format's exact treeBottomUp contract, MESSAGE_STATUS_* statics).

Verified end to end against the real backend: used the still-functional old
app (a second account, ixp355087) to create a real friendship and exchange
messages with the new app's test account, confirming the new chat list and
conversation view correctly render pre-existing real data, sending a new
message shows the right optimistic-then-delivered status transition, and
the old app receives it live in return.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/lib/tinode/send.ts

@@ -0,0 +1,32 @@
+import { Drafty, type DraftyContent, type StoredMessage, type Topic } from 'tinode-sdk';
+
+/**
+ * Plain-text send: createMessage + publishDraft (not the simpler `.publish()`), matching the old
+ * app's own choice -- publishDraft inserts the message into the local cache and fires onData
+ * immediately, showing "sending" before the network round trip resolves, rather than waiting on it.
+ */
+export function sendText(topic: Topic, text: string, head?: Record<string, unknown>): Promise<unknown> {
+  const parsed = Drafty.parse(text);
+  const content: DraftyContent | string = Drafty.isPlainText(parsed) ? text : parsed;
+  const msg = topic.createMessage(content, false);
+  if (head) msg.head = Object.assign(msg.head || {}, head);
+  return topic.publishDraft(msg, Promise.resolve());
+}
+
+/**
+ * Retries a failed send by flushing the old local entry and building+publishing a fresh one with
+ * the same content/head -- ported from the old app's context-menu "重试" handler (context-menu.jsx),
+ * not a simple re-publish of the same object. Returns undefined if `seq` is no longer in the local
+ * cache (already flushed, or never existed).
+ */
+export function retryMessage(topic: Topic, seq: number): Promise<unknown> | undefined {
+  const failed = topic.flushMessage(seq);
+  if (!failed) return undefined;
+  const msg = topic.createMessage((failed.content as DraftyContent | string) ?? '', false);
+  if (failed.head) msg.head = Object.assign(msg.head || {}, failed.head);
+  return topic.publishDraft(msg, Promise.resolve());
+}
+
+export function messageIsMine(msg: StoredMessage, myUserId: string | null): boolean {
+  return !!myUserId && msg.from === myUserId;
+}