fix(client): clean up leftover pre-TerminalView dead code and type errors in Workspace.tsx

`npm run test:client` (Vitest/esbuild) doesn't type-check, so several
tasks' incomplete cleanup of the old RunConsole-era code in
Workspace.tsx (SlashCommand/BUILTIN_SLASH_COMMANDS references, old
RunStatus values, a stray `mode` field, a wrong `prompt` vs
`initialPrompt` key) went unnoticed through every review until `tsc
--noEmit` was run directly. Also fixes a stale `RunStatusPayload.exitCode`
read in Tabby's brain.ts and dangling RunStreamPayload/RunInputAckPayload
references left in types.ts.

client/src/pages/SessionDetail.tsx

@@ -218,9 +218,7 @@ export function SessionDetail() {
         .list()
         .then((r) => {
           if (cancelled) return;
-          const live = r.items.some(
-            (h) => h.sessionId === id && (h.status === "running" || h.status === "spawning")
-          );
+          const live = r.items.some((h) => h.sessionId === id && h.status === "running");
           setIsDashboardRun(live);
         })
         .catch(() => undefined);