feat(tui): auto-correct base URL if required path suffix is missing

Providers that need /v1 (lmstudio, llamacpp, qwen) now declare a
url_suffix field. The AI settings save action appends it automatically
and notifies the user if they entered a URL without it.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pyra/config/tui.py

@@ -171,6 +171,15 @@ class _AITab(VerticalScroll):
         base_url    = self.query_one("#ai-base-url", Input).value.strip() or None
         api_key     = self.query_one("#ai-key", Input).value.strip()
 
+        if base_url and provider.url_suffix and not base_url.rstrip("/").endswith(provider.url_suffix):
+            base_url = base_url.rstrip("/") + provider.url_suffix
+            self.query_one("#ai-base-url", Input).value = base_url
+            self.app.notify(
+                f"Base URL must end with '{provider.url_suffix}' for {provider.display_name} — corrected automatically.",
+                severity="warning",
+                timeout=6,
+            )
+
         cfg = load_config()
         cfg.ai.provider_id = provider_id
         cfg.ai.model = model