feat(web): add Console (stderr) tab; show it on stdio connect failure (#1621)

A failed stdio launch had no useful diagnostic surface: the message log
(History) is cleared on the error transition and there are no HTTP
requests (Network), so the auto-opened monitoring column was empty. The
process's stderr — which explains the failure (e.g. "No module named
mcp_server_time") — was captured in StderrLogState but never displayed.

- New ConsoleScreen renders the captured stderr stream (search / sort /
  clear / export; embeddable in the monitoring column), wired through App
  via the existing useStderrLog hook + StderrLogState.
- Console is a pinnable monitor tab like Logs/History/Network, gated to
  stdio servers (HTTP has no child process). It lives in the header menu
  when the column isn't pinned, and moves into the column when it is.
- The failure column now picks its tabs by which diagnostic actually
  captured content (stderr → Console, fetch requests → Network), not by
  the active server's transport: a connect failure fires the client
  `disconnect` event, which clears `activeServer`, so transport can't be
  read back there. The memo re-runs as stderr/fetch entries stream in, so
  the diagnostic tab appears as soon as the failing process prints.

Verified live against a failing `python -m mcp_server_time` stdio server:
the column auto-opens to Console showing the real ModuleNotFoundError.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BrihGWcrM9JGRyu41nzZYw

clients/web/src/theme/Text.ts

@@ -26,6 +26,17 @@ export const ThemeText = Text.extend({
         },
       };
     }
+    // A line of captured server stderr (#1621): preserve the process's own
+    // newlines/whitespace (`pre-wrap`) while still wrapping over-long lines
+    // inside the narrow monitoring column (`break-word`).
+    if (props.variant === "consoleLine") {
+      return {
+        root: {
+          whiteSpace: "pre-wrap",
+          wordBreak: "break-word",
+        },
+      };
+    }
     return { root: {} };
   },
 });