ref(explorer): cleanup UI interrupt state and panel code

[aliu39]

Code organization and cleanup for explorer chat UI, before implementing a polling timeout. Should not affect current functionality.

Refactors:

• Use helpers _onNewRequest and _onRequestError for repeated interrupt/waiting state management in useSeerExplorer. This will soon include timeout state

• Moves the "response complete" detection from inline code (ran every render) into a useEffect. In general we could use a lot less useEffect's but seems correct here - reducing effects is a larger refactor for another day

• Simplifies interrupt detection by removing the prevInterruptRequestedRef approach — wasJustInterrupted is now set directly when polling stops after an interrupt request.

• startNewSession delegates to switchToRun(null) to deduplicate code

• Simplifies the readOnly computation in explorerPanel by removing defensive type-checking around useUser(). The comment is not accurate

• Simplify props for disabled textarea in case of read-only

Cleanup:

• Removes the always-poll-when-drawer-open (isSeerDrawerOpen) condition. Chat is no longer embedded into seer drawer.

• Removes clearWasJustInterrupted from hook API. Clearing on user request + switch session is sufficient

• Removes isPending from the hook's return value (unused externally and not useful due to polling)

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Premature polling stop when session data is null
  • Added explicit check for filteredSessionData in useEffect condition to ensure waitingForResponse is only cleared when session data actually exists and is not loading.

Or push these changes by commenting:

@cursor push 0f6a2c5c44

Preview (0f6a2c5c44)

diff --git a/static/app/views/seerExplorer/hooks/useSeerExplorer.tsx b/static/app/views/seerExplorer/hooks/useSeerExplorer.tsx
--- a/static/app/views/seerExplorer/hooks/useSeerExplorer.tsx
+++ b/static/app/views/seerExplorer/hooks/useSeerExplorer.tsx
@@ -563,7 +563,7 @@
       filteredSessionData.blocks.some((block: Block) => block.loading));
 
   useEffect(() => {
-    if (waitingForResponse && !isLoading) {
+    if (waitingForResponse && filteredSessionData && !isLoading) {
       // Stop waiting once we see the response is no longer loading
       setWaitingForResponse(false);
       // Clear deleted index once response is complete
@@ -574,7 +574,7 @@
         setWasJustInterrupted(true); // set persistent UI flag until next request
       }
     }
-  }, [waitingForResponse, interruptRequested, isLoading]);
+  }, [waitingForResponse, interruptRequested, isLoading, filteredSessionData]);
 
   return {
     sessionData: filteredSessionData,

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