fix: add actionable hint for OpenRouter 'no tool endpoints' error

When OpenRouter returns 'No endpoints found that support tool use'
(HTTP 404), display a hint explaining that provider routing restrictions
may be filtering out tool-capable providers. Links the user directly
to the model's OpenRouter page to check which providers support tools.

The hint fires in the error display block that runs regardless of whether
fallback succeeds — so the user always understands WHY the model failed,
not just that it fell back.

Reported via Discord: GLM-5.1 on OpenRouter with US-based provider
restrictions eliminated all 4 tool-supporting endpoints (DeepInfra,
Z.AI, Friendli, Venice), leaving only 7 non-tool providers.

run_agent.py

@@ -8233,7 +8233,33 @@ class AIAgent:
                         if _err_body_str:
                             self._vprint(f"{self.log_prefix}   📋 Details: {_err_body_str}", force=True)
                     self._vprint(f"{self.log_prefix}   ⏱️  Elapsed: {elapsed_time:.2f}s  Context: {len(api_messages)} msgs, ~{approx_tokens:,} tokens")
-                    
+
+                    # Actionable hint for OpenRouter "no tool endpoints" error.
+                    # This fires regardless of whether fallback succeeds — the
+                    # user needs to know WHY their model failed so they can fix
+                    # their provider routing, not just silently fall back.
+                    if (
+                        self._is_openrouter_url()
+                        and "support tool use" in error_msg
+                    ):
+                        self._vprint(
+                            f"{self.log_prefix}   💡 No OpenRouter providers for {_model} support tool calling with your current settings.",
+                            force=True,
+                        )
+                        if self.providers_allowed:
+                            self._vprint(
+                                f"{self.log_prefix}      Your provider_routing.only restriction is filtering out tool-capable providers.",
+                                force=True,
+                            )
+                            self._vprint(
+                                f"{self.log_prefix}      Try removing the restriction or adding providers that support tools for this model.",
+                                force=True,
+                            )
+                        self._vprint(
+                            f"{self.log_prefix}      Check which providers support tools: https://openrouter.ai/models/{_model}",
+                            force=True,
+                        )
+
                     # Check for interrupt before deciding to retry
                     if self._interrupt_requested:
                         self._vprint(f"{self.log_prefix}⚡ Interrupt detected during error handling, aborting retries.", force=True)