v0.7.12: Custom models/providers support via models.json

- Add ~/.pi/agent/models.json config for custom providers (Ollama, vLLM, etc.)
- Support all 4 API types (openai-completions, openai-responses, anthropic-messages, google-generative-ai)
- Live reload models.json on /model selector open
- Smart model defaults per provider (claude-sonnet-4-5, gpt-5.1-codex, etc.)
- Graceful session fallback when saved model missing or no API key
- Validation errors show precise file/field info in CLI and TUI
- Agent knows its own README.md path for self-documentation
- Added gpt-5.1-codex (400k context, 128k output, reasoning)

Fixes #21

packages/coding-agent/src/settings-manager.ts

@@ -4,6 +4,8 @@ import { dirname, join } from "path";
 
 export interface Settings {
 	lastChangelogVersion?: string;
+	defaultProvider?: string;
+	defaultModel?: string;
 }
 
 export class SettingsManager {
@@ -52,4 +54,28 @@ export class SettingsManager {
 		this.settings.lastChangelogVersion = version;
 		this.save();
 	}
+
+	getDefaultProvider(): string | undefined {
+		return this.settings.defaultProvider;
+	}
+
+	getDefaultModel(): string | undefined {
+		return this.settings.defaultModel;
+	}
+
+	setDefaultProvider(provider: string): void {
+		this.settings.defaultProvider = provider;
+		this.save();
+	}
+
+	setDefaultModel(modelId: string): void {
+		this.settings.defaultModel = modelId;
+		this.save();
+	}
+
+	setDefaultModelAndProvider(provider: string, modelId: string): void {
+		this.settings.defaultProvider = provider;
+		this.settings.defaultModel = modelId;
+		this.save();
+	}
 }