feat(agents): Show when Claude Code retries a failed API request (#214)

When Claude Code loses its API connection or is refused, it retries on its own
for up to several minutes. The session showed only "Working…" meanwhile. It
now shows "API request failed, retrying in Ns (attempt 3/10)" with the error
in the tooltip, cleared by the agent's next output or the end of the turn.

src/features/agents/Session.module.css

@@ -437,6 +437,10 @@
   color: var(--fg-muted);
 }
 
+.retrying {
+  color: var(--warning);
+}
+
 .composerArea {
   flex: none;
   display: flex;