feat(chat): focus the composer when the Chat tab opens

ChatPanel remounts on every tab switch, so a mount effect is the tab-entry
hook. `focus({ preventScroll: true })` so it does not fight the panel-sizing
and scroll-to-bottom effects still settling, and so a phone opens the
keyboard without the view jumping.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018gKJ85aZyvEwarXMFzFEwi

1 files changed, 10 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/chat-app.js b/packages/meshbay-hub/src/meshbay_hub/static/chat-app.js
index 3d518b3..f21ec2c 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/chat-app.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/chat-app.js
@@ -316,6 +316,16 @@ function ChatPanel({ transportRef, username, entries, gekRef, onRefreshIndex,
     return () => ro.disconnect();
   }, [messages]);
 
+  // Entering the Chat tab should leave the cursor in the composer, ready to
+  // type — the panel mounts fresh on every tab switch, so a mount effect is
+  // the tab-entry hook. `preventScroll` because the layout effects above are
+  // still settling the panel height and a focus-driven scroll would fight
+  // them; on a phone this also means the keyboard opens without the view
+  // jumping.
+  useEffect(() => {
+    inputRef.current?.focus({ preventScroll: true });
+  }, []);
+
   // The panel was `calc(100vh - 220px)`: a guess at how much sits above it. On a
   // phone the group header — title, description, edit link, delete button, tabs
   // — is closer to 430px, so the panel ran past the fold and the composer ended