Fix ui jitter during remote server initialization (#9342)

## Description
* Fixes
[APP-4307](https://linear.app/warpdotdev/issue/APP-4307/fix-blocklist-ui-flicker-when-initializing-remote-server)
* The issue: during the initialization flow there would be significant
ui jitter where the entire blocklist is moving up and down - this is
because there is a gap between when the command/init shell finishes and
when we render the loading footer (which looks like the output grid
cursor appearing, then disappearing, then the loading footer appearing)
* The fix is to render the footer as we're checking for if the binary is
installed so that there is no gap for when the cursor disappears and the
loading footer appears
* The original reason this was done was to ensure that the loading
footer didn't appear before or with the choice block - I've updated it
to have an explicit check instead
* This also updates where we're handling `RemoteServerSetupStateChanged`
such that `session` is able to handle and update itself, and the
terminal view is only in charge of rerendering the footer

## Testing
https://www.loom.com/share/d4f157b4afd94f648f61ab1afbcee249

## Agent Mode
- [x] Warp Agent Mode - This PR was created via Warp's AI Agent Mode

crates/remote_server/src/setup.rs

@@ -37,10 +37,6 @@ impl RemoteServerSetupState {
             Self::Checking | Self::Installing { .. } | Self::Initializing
         )
     }
-
-    pub fn is_connecting(&self) -> bool {
-        matches!(self, Self::Installing { .. } | Self::Initializing)
-    }
 }
 
 /// Detected remote platform from `uname -sm` output.