feat(config): add Copilot configuration options

- Add Copilot section with agent-initiator-persist flag
- Add scanner buffer size configuration
- Add account type configuration option
- Document configuration options in example config

Author: jeffnash

config.example.yaml

@@ -127,6 +127,26 @@ ws-auth: false
 #    # long-running agent interactions and helps prevent hitting standard rate limits.
 #    agent-initiator-persist: true
 
+# GitHub Copilot account configuration
+# Note: Copilot uses OAuth device code authentication, NOT API keys or tokens.
+# Do NOT paste your GitHub access token or Copilot bearer token here.
+# Tokens are stored only in auth-dir JSON files, never in config.yaml.
+#
+# To authenticate:
+#   - CLI: run with -copilot-login flag
+#   - Web: use the /copilot-auth-url management endpoint
+#
+# After OAuth login, tokens are managed automatically and stored in auth-dir.
+# The entries below only configure account type and optional proxy settings.
+#copilot-api-key:
+#  - account-type: "individual" # Options: individual, business, enterprise
+#    proxy-url: "socks5://proxy.example.com:1080" # optional: proxy for Copilot requests
+
+#    # When set to true, this flag forces subsequent requests in a session (sharing the same prompt_cache_key)
+#    # to send the header "X-Initiator: agent" instead of "vscode". This mirrors VS Code's behavior for
+#    # long-running agent interactions and helps prevent hitting standard rate limits.
+#    agent-initiator-persist: true
+
 # Claude API keys
 #claude-api-key:
 #  - api-key: "sk-atSM..." # use the official claude API key, no need to set the base url

internal/config/config.go

@@ -231,6 +231,21 @@ type CopilotKey struct {
 	AgentInitiatorPersist bool `yaml:"agent-initiator-persist" json:"agent-initiator-persist"`
 }
 
+// CopilotKey represents the configuration for GitHub Copilot API access.
+// Authentication is handled via device code OAuth flow, not API keys.
+type CopilotKey struct {
+	// AccountType is the Copilot subscription type (individual, business, enterprise).
+	// Defaults to "individual" if not specified.
+	AccountType string `yaml:"account-type" json:"account-type"`
+
+	// ProxyURL overrides the global proxy setting for Copilot requests if provided.
+	ProxyURL string `yaml:"proxy-url,omitempty" json:"proxy-url,omitempty"`
+
+	// AgentInitiatorPersist, when true, forces subsequent Copilot requests sharing the
+	// same prompt_cache_key to send X-Initiator=agent after the first call. Default false.
+	AgentInitiatorPersist bool `yaml:"agent-initiator-persist" json:"agent-initiator-persist"`
+}
+
 // GeminiKey represents the configuration for a Gemini API key,
 // including optional overrides for upstream base URL, proxy routing, and headers.
 type GeminiKey struct {