fix: add strict:false to Responses API tools and gpt-5.4 to known models (#8636)

Signed-off-by: Bradley Axen <baxen@squareup.com>

crates/goose-test-support/src/session.rs

@@ -1,7 +1,12 @@
 use std::sync::{Arc, Mutex};
 
 pub const TEST_SESSION_ID: &str = "test-session-id";
-pub const TEST_MODEL: &str = "gpt-5-nano";
+// Use a Chat Completions model so the canned SSE fixtures (which return
+// Chat Completions format) are parsed correctly. gpt-5-nano now routes to
+// the Responses API which needs a different mock format.
+// TODO: add a Responses API mock to OpenAiFixture so tests can cover
+// responses-routed models like gpt-5-nano end-to-end.
+pub const TEST_MODEL: &str = "gpt-4.1";
 
 const NOT_YET_SET: &str = "session-id-not-yet-set";
 pub(crate) const SESSION_ID_HEADER: &str = "agent-session-id";