Remove GitHub Copilot provider support

Remove all GitHub Copilot integration from the codebase to streamline
the supported provider set to OpenAI, OpenRouter, Anthropic, and Ollama.

Changes:
- Delete core Copilot implementation (copilot.go) and all related tests
- Remove Copilot configuration fields from App struct and Config
- Remove Copilot from provider factory and API key handling
- Update all test files to replace Copilot references with other providers
- Remove Copilot documentation from README, configuration guide, and examples
- Remove Copilot section from config.toml.example

All tests pass successfully after removal.

Co-authored-by: Cursor <cursoragent@cursor.com>

3 files changed, 5 insertions, 20 deletions

diff --git a/internal/lsp/handlers_utils.go b/internal/lsp/handlers_utils.go
index 6260acd..1ea36c8 100644
--- a/internal/lsp/handlers_utils.go
+++ b/internal/lsp/handlers_utils.go
@@ -110,8 +110,6 @@ func resolveDefaultModel(cfg appconfig.App, provider string) string {
 	switch provider {
 	case "ollama":
 		return strings.TrimSpace(cfg.OllamaModel)
-	case "copilot":
-		return strings.TrimSpace(cfg.CopilotModel)
 	case "anthropic":
 		return strings.TrimSpace(cfg.AnthropicModel)
 	case "openrouter":
diff --git a/internal/lsp/llm_request_opts_test.go b/internal/lsp/llm_request_opts_test.go
index f4d31b9..ad87cd4 100644
--- a/internal/lsp/llm_request_opts_test.go
+++ b/internal/lsp/llm_request_opts_test.go
@@ -44,10 +44,10 @@ func TestBuildRequestSpecs_MultiEntries(t *testing.T) {
 	s := newTestServer()
 	s.cfg.CompletionConfigs = []appconfig.SurfaceConfig{
 		{Provider: "openai", Model: "gpt-4o"},
-		{Provider: "copilot", Model: "cpt", Temperature: floatPtr(0.4)},
+		{Provider: "anthropic", Model: "claude", Temperature: floatPtr(0.4)},
 	}
 	s.cfg.OpenAIModel = "gpt-3.5"
-	s.cfg.CopilotModel = "cpt-base"
+	s.cfg.AnthropicModel = "claude-base"
 	s.cfg.MaxTokens = 256
 	specs := s.buildRequestSpecs(surfaceCompletion)
 	if len(specs) != 2 {
@@ -56,7 +56,7 @@ func TestBuildRequestSpecs_MultiEntries(t *testing.T) {
 	if specs[0].provider != "openai" || specs[0].index != 0 {
 		t.Fatalf("unexpected first spec: %+v", specs[0])
 	}
-	if specs[1].provider != "copilot" || specs[1].index != 1 {
+	if specs[1].provider != "anthropic" || specs[1].index != 1 {
 		t.Fatalf("unexpected second spec: %+v", specs[1])
 	}
 	var opts1, opts2 llm.Options
@@ -69,7 +69,7 @@ func TestBuildRequestSpecs_MultiEntries(t *testing.T) {
 	if opts1.Model != "gpt-4o" || opts1.MaxTokens != 256 {
 		t.Fatalf("unexpected opts1: %+v", opts1)
 	}
-	if opts2.Model != "cpt" || opts2.Temperature != 0.4 {
+	if opts2.Model != "claude" || opts2.Temperature != 0.4 {
 		t.Fatalf("unexpected opts2: %+v", opts2)
 	}
 }
diff --git a/internal/lsp/server.go b/internal/lsp/server.go
index bbee64f..c226ab4 100644
--- a/internal/lsp/server.go
+++ b/internal/lsp/server.go
@@ -230,9 +230,6 @@ func newClientForProvider(cfg appconfig.App, provider string) (llm.Client, error
 		OllamaBaseURL:         cfg.OllamaBaseURL,
 		OllamaModel:           cfg.OllamaModel,
 		OllamaTemperature:     cfg.OllamaTemperature,
-		CopilotBaseURL:        cfg.CopilotBaseURL,
-		CopilotModel:          cfg.CopilotModel,
-		CopilotTemperature:    cfg.CopilotTemperature,
 		AnthropicBaseURL:      cfg.AnthropicBaseURL,
 		AnthropicModel:        cfg.AnthropicModel,
 		AnthropicTemperature:  cfg.AnthropicTemperature,
@@ -245,15 +242,11 @@ func newClientForProvider(cfg appconfig.App, provider string) (llm.Client, error
 	if orKey == "" {
 		orKey = strings.TrimSpace(os.Getenv("OPENROUTER_API_KEY"))
 	}
-	cpKey := strings.TrimSpace(os.Getenv("HEXAI_COPILOT_API_KEY"))
-	if cpKey == "" {
-		cpKey = strings.TrimSpace(os.Getenv("COPILOT_API_KEY"))
-	}
 	anKey := strings.TrimSpace(os.Getenv("HEXAI_ANTHROPIC_API_KEY"))
 	if anKey == "" {
 		anKey = strings.TrimSpace(os.Getenv("ANTHROPIC_API_KEY"))
 	}
-	return llm.NewFromConfig(llmCfg, oaKey, orKey, cpKey, anKey)
+	return llm.NewFromConfig(llmCfg, oaKey, orKey, anKey)
 }
 
 func (s *Server) clientFor(spec requestSpec) llm.Client {
@@ -296,12 +289,6 @@ func (s *Server) clientFor(spec requestSpec) llm.Client {
 		} else if spec.fallbackModel != "" {
 			cfg.OpenRouterModel = spec.fallbackModel
 		}
-	case "copilot":
-		if modelOverride != "" {
-			cfg.CopilotModel = modelOverride
-		} else if spec.fallbackModel != "" {
-			cfg.CopilotModel = spec.fallbackModel
-		}
 	case "ollama":
 		if modelOverride != "" {
 			cfg.OllamaModel = modelOverride