chat: read receipts (delivered + seen) and persisted active bucket

Read receipts on chat messages — single check for delivered (recipient
polled), double check for seen (recipient opened the thread). Pending
state shows a clock until the relay acks the post.

Relay (relay/):
* bootstrap.php: ALTER TABLE chat_messages ADD COLUMN seen + a
  (sender_id, id) index for the sender-side state poll. Migration is
  idempotent via PRAGMA table_info.
* routes/chat.php: two new routes
  - GET  /api/chat/sent?since=N — returns the receipt state (id,
    recipient_id, fetched, seen, created_at) for messages the caller
    sent. No body — sender already has the plaintext locally.
  - POST /api/chat/seen { peer } — marks every message FROM peer TO
    caller as seen=1. Idempotent. Frontend calls this when opening
    a thread; sender's next /sent poll picks the new state up.

Plugin backend (public/plugins/chat/backend.php):
* schema migration: chat_messages gets `delivered` and `seen` columns
  (idempotent), only meaningful for direction='out'.
* /api/chat/send: stores the relay's autoincrement id as `relay_id`
  on the local outgoing row so the receipt poll can match against it.
* /api/chat/poll: after the normal incoming pull, also calls
  GET /api/chat/sent?since=last_sent_relay_id and updates local
  outgoing rows with delivered/seen via UPDATE WHERE relay_id. The
  cursor (last_sent_relay_id state value) only advances past rows
  whose state is final (seen=1); rows still in flight stay re-pollable.
  Response now carries `receipts: <count>` so the frontend can refresh
  the open thread when state changes without new incoming.
* /api/chat/read: after the local is_read=1 update, fires a POST to
  the relay's /api/chat/seen so the sender gets the double-check.
  Silent on failure — the user already saw the messages locally.
* /api/chat/messages: SELECT now includes delivered, seen.

Plugin frontend (public/plugins/chat/chat.js):
* renderThread() appends a receipt icon to outgoing bubbles:
  - seen=1                      → ph-checks (accent, double check)
  - delivered=1, seen=0         → ph-check  (muted, single check)
  - both 0                       → ph-clock  (dim, pending)
  Incoming messages get nothing.
* pollOnce() refreshes the open thread when receipts > 0 even with
  no new incoming, so the icons update in real time while the user
  is looking at the thread.

CSS (public/plugins/chat/chat.css):
* .chat-bubble-time becomes flex with gap so timestamp + receipt
  icon sit on one line.
* .chat-receipt.pending / .delivered / .seen color tiers.

board: persist active bucket across reloads

* state.js: state.activeBucket initializes from
  localStorage.getItem('hyprcrd-active-bucket') || 'all'. New
  setActiveBucket(value) helper writes through to localStorage; new
  ensureActiveBucketValid() helper falls back to 'all' if the
  persisted id no longer exists in state.buckets.
* buckets.js: loadBuckets() calls ensureActiveBucketValid() right
  after the API fetch and before renderBar(). All four production
  assignments (delete-keep, delete-all, popover entry click, regular
  tab click) replaced with setActiveBucket() so the persisted value
  stays in sync. Tests still mutate state.activeBucket directly so
  they don't touch localStorage.

chore: bump version to 0.9.6

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

public/plugins/chat/chat.js

@@ -231,9 +231,18 @@ function renderThread() {
     if (!wrap) return;
     wrap.innerHTML = currentMessages.map(m => {
         const cls = m.direction === 'out' ? 'out' : 'in';
+        // Read receipts for outgoing messages: single check = recipient
+        // polled (delivered), double check = recipient opened the thread
+        // (seen). Incoming messages get no icon.
+        let receipt = '';
+        if (m.direction === 'out') {
+            if (Number(m.seen)) receipt = '<i class="ph ph-checks chat-receipt seen"></i>';
+            else if (Number(m.delivered)) receipt = '<i class="ph ph-check chat-receipt delivered"></i>';
+            else receipt = '<i class="ph ph-clock chat-receipt pending"></i>';
+        }
         return `
             <div class="chat-bubble ${cls}">${escapeHtml(m.body)}</div>
-            <div class="chat-bubble-time">${escapeHtml(formatChatTime(m.sent_at))}</div>
+            <div class="chat-bubble-time">${escapeHtml(formatChatTime(m.sent_at))}${receipt}</div>
         `;
     }).join('');
     // Scroll to bottom
@@ -330,6 +339,7 @@ async function pollOnce() {
         const res = await hyprcrd.api('api/chat/poll', { method: 'POST' }).catch(() => null);
         if (!res?.ok) return;
         const newCount = res.new || 0;
+        const receiptUpdates = res.receipts || 0;
         if (newCount > 0) {
             await loadConversations();
             // If we're inside a thread for any peer, refresh + auto-read it
@@ -340,6 +350,10 @@ async function pollOnce() {
             }
             // Blink if the flyout is closed
             if (!isOpen()) startBlink();
+        } else if (receiptUpdates > 0 && isOpen() && currentPeer) {
+            // No new incoming, but receipts (delivered/seen) changed for
+            // our outgoing — refresh the thread so the check icons update.
+            await loadThread(currentPeer);
         } else if (initialPollDone === false) {
             // First poll: refresh badges in case we have unread from a previous session
             await loadConversations();