Give the transcript a way back, and stop losing an import's name

**Every imported session was called "claude-cli session".** The app has
nothing to say about the title -- the server names it after the session it
is continuing -- so it sent `""`. That is `Some`, which satisfied the
`or_else` meant to catch "no title given", so the imported name was
computed and then thrown away in favour of the `<provider> session`
fallback.

Normalised at the boundary instead: blank means absent, because that is
what it means to the person who left it blank. Both the client's value and
the imported one go through the same trim, so neither can be a string of
spaces standing in for a name.

**And a jump-to-latest button**, shown only while the newest message is
off-screen. Reading back through a conversation is a place to be rather
than a state to be rescued from, so it waits to be wanted and leaves once
there is nowhere to jump to.

It says where it goes instead of drawing an arrow. The list is laid out
from the bottom, so "down" in the data is up on the screen, and an arrow
would be asking the reader to hold that in their head to press a button.

Verified on screen: an import now arrives titled "ai-app" rather than
"claude-cli session", and the button appears on scrolling back, returns to
the newest message, and disappears on arrival.

server/src/routes.rs

@@ -489,11 +489,21 @@ async fn spawn_session(
         provider: body.provider,
         // An imported session is recognised by what it was about, so its
         // opening message is the title unless one was typed.
-        title: body.title.or_else(|| {
-            seed.as_ref()
-                .map(|(chosen, _)| chosen.title.clone())
-                .filter(|title| !title.is_empty())
-        }),
+        // Blank normalised to absent here rather than trusted as a
+        // choice. A client with nothing to say sends `""`, which is
+        // `Some` and so satisfied `or_else` -- the imported session's real
+        // title was computed, then discarded in favour of the "<provider>
+        // session" fallback, so every import arrived called "claude-cli
+        // session". Absent and empty mean the same thing to a person and
+        // have to mean the same thing here.
+        title: body
+            .title
+            .filter(|title| !title.trim().is_empty())
+            .or_else(|| {
+                seed.as_ref()
+                    .map(|(chosen, _)| chosen.title.clone())
+                    .filter(|title| !title.trim().is_empty())
+            }),
         model: body.model,
         // Resumed where it was working, so the CLI picks up the same tree.
         cwd: body.cwd.or_else(|| {