feat(ollama): OLLAMA_BASE_URL end-to-end with endpoint confirmation

OLLAMA_BASE_URL now flows through both the CLI dropdown and the
programmatic client (call-time evaluation so tests behave). After
provider selection, the CLI prints the resolved endpoint and marks
when it came from the env var, plus a soft warning when the URL is
missing a scheme or non-default port. Drops the stale "(local)"
suffix from Ollama model labels since the endpoint is now dynamic.

.env.example

@@ -12,6 +12,12 @@ MINIMAX_API_KEY=
 MINIMAX_CN_API_KEY=
 OPENROUTER_API_KEY=
 
+# Optional: point at a remote Ollama server. When unset, defaults to
+# the local instance at http://localhost:11434/v1. Convention follows
+# the broader Ollama ecosystem; both the CLI dropdown and programmatic
+# client pick this up.
+#OLLAMA_BASE_URL=http://your-ollama-host:11434/v1
+
 # Optional: override DEFAULT_CONFIG without editing code.
 # Any TRADINGAGENTS_* variable below, when set, replaces the matching key
 # in tradingagents/default_config.py. Values are coerced to the type of