feat: initial model catalog with 196 models across 39 providers

Community-maintained TOML catalog for LibreFang. New models can be added
via PR without requiring a LibreFang binary release.

Includes validation script, bilingual docs, and GitHub templates.

providers/github-copilot.toml

@@ -0,0 +1,35 @@
+# GitHub Copilot — https://github.com/features/copilot
+# Models: 2 (free for GitHub Copilot subscribers)
+
+[provider]
+id = "github-copilot"
+display_name = "GitHub Copilot"
+api_key_env = "GITHUB_TOKEN"
+base_url = "https://api.githubcopilot.com"
+key_required = true
+
+[[models]]
+id = "copilot/gpt-4o"
+display_name = "GPT-4o (Copilot)"
+tier = "smart"
+context_window = 128000
+max_output_tokens = 4096
+input_cost_per_m = 0.0
+output_cost_per_m = 0.0
+supports_tools = true
+supports_vision = true
+supports_streaming = true
+aliases = ["copilot-gpt4o"]
+
+[[models]]
+id = "copilot/gpt-4"
+display_name = "GPT-4 (Copilot)"
+tier = "frontier"
+context_window = 128000
+max_output_tokens = 4096
+input_cost_per_m = 0.0
+output_cost_per_m = 0.0
+supports_tools = true
+supports_vision = false
+supports_streaming = true
+aliases = ["copilot-gpt4"]