fix(workspace): restore View button functionality and clean up dead props

Fix two issues identified in code review:

1. Critical: onViewFromHistory was a silent no-op. Now navigates to the
   SessionDetail page using the same route pattern as the external link in
   RunHistory, allowing users to view a finished run's transcript.

2. Important: Removed dead slashCommands={[]} prop from RunSetup invocation.
   Made slashCommands optional in RunSetupProps to maintain type safety while
   reflecting that the discovery logic was removed.

All tests pass (396 client, 1152 server).

client/src/components/run/RunSetup.tsx

@@ -112,7 +112,7 @@ interface RunSetupProps {
    *  sessions. Undefined when no lane is selected (the picker then lists
    *  everything, same as before lanes existed). */
   laneCwd?: string;
-  slashCommands: SlashCommand[];
+  slashCommands?: SlashCommand[];
   runHistory: DashboardRunHistoryItem[];
   onResumeFromHistory: (item: DashboardRunHistoryItem) => void;
 }
@@ -172,7 +172,7 @@ export function RunSetup(props: RunSetupProps) {
           onSubmit={() => handleStart(props)}
           placeholder={t("fields.promptPlaceholderTerminal")}
           rows={5}
-          slashCommands={props.slashCommands}
+          slashCommands={props.slashCommands ?? []}
           fileCwd={props.resumeSession?.cwd || props.cwd}
         />
         <div className="mt-1 text-[10px] text-fg-muted">