feat: add Gemini CLI, Codex CLI, and Aider provider catalogs (#7)

- gemini-cli: Google Gemini CLI (gemini-2.5-pro, gemini-2.5-flash)
- codex-cli: OpenAI Codex CLI (o4-mini, o3, gpt-4.1)
- aider: Aider AI coding assistant (sonnet, gpt-4o)

providers/aider.toml

@@ -0,0 +1,34 @@
+[provider]
+id = "aider"
+display_name = "Aider"
+api_key_env = ""
+base_url = ""
+key_required = false
+
+[[models]]
+id = "aider/sonnet"
+display_name = "Claude Sonnet via Aider"
+provider = "aider"
+tier = "smart"
+context_window = 200000
+max_output_tokens = 64000
+input_cost_per_m = 0.0
+output_cost_per_m = 0.0
+supports_tools = false
+supports_vision = false
+supports_streaming = false
+aliases = ["aider-sonnet"]
+
+[[models]]
+id = "aider/gpt-4o"
+display_name = "GPT-4o via Aider"
+provider = "aider"
+tier = "smart"
+context_window = 128000
+max_output_tokens = 16384
+input_cost_per_m = 0.0
+output_cost_per_m = 0.0
+supports_tools = false
+supports_vision = false
+supports_streaming = false
+aliases = ["aider-gpt-4o"]