fix(site): fall back to chat detail cache for archive-and-delete confirmation - #25055

Closes CODAGT-317 (partially — see Caveat below).

Problem

The "Archive agent & delete workspace" molly-guard (typing the workspace name) was firing inconsistently for chats whose workspaces were clearly auto-provisioned. The heuristic in resolveArchiveAndDeleteAction is:

if (chatCreatedAt && isWorkspaceAutoCreated(workspace.created_at, chatCreatedAt)) {
  return "proceed";
}
return "confirm";

The chatCreatedAt callback only read from the infinite chat-list cache:

() =>
  readInfiniteChatsCache(queryClient)?.find((c) => c.id === chatId)?.created_at,

If the chat row wasn't in a currently-loaded page of the infinite list query (different filter active, scrolled past the loaded pages, or invoked from a context where the sidebar list wasn't materialized for that chat), the lookup returned undefined, the chatCreatedAt && ... short-circuited to false, and the dialog was shown regardless of who created the workspace. From the user's perspective the molly-guard appeared at random.

Fix

Fall back to the per-chat detail cache (chatKey(chatId)) when the list cache misses. That cache is populated whenever the user has visited the chat — which is essentially always true in the archive-and-delete flow.

() =>
  readInfiniteChatsCache(queryClient)?.find((c) => c.id === chatId)
    ?.created_at ??
  queryClient.getQueryData<TypesGen.Chat>(chatKey(chatId))?.created_at,

The resolver itself is unchanged — the existing "chat not found in cache → confirm" test still holds. Only the call site widens where it looks for created_at.

Caveat

This fixes one source of the false-positive dialog (cache miss). There are reports of the dialog still firing after a full page reload with the chat open, which would not be addressed by this change — those cases likely involve a workspace whose created_at genuinely predates the chat's created_at (e.g. rebound to a pre-existing workspace, or a recreated-with-same-name workspace whose timestamp comparison goes the wrong way). Diagnostic info is being collected for that path; a more durable fix is in flight in #25053 which replaces the timestamp heuristic with an explicit workspace_auto_created column.

Test plan

• pnpm lint:types passes.
• pnpm vitest run --project=unit src/pages/AgentsPage/utils/agentWorkspaceUtils.test.ts — 28/28 pass; existing "chat not found in cache → confirm" case still covers the both-caches-miss scenario.
• pnpm biome check passes on the changed file.

Created on behalf of @kylecarbs (reported) and @johnstcn (asked for the PR).