feat: enhance model cycling with thinking levels and --thinking flag

PR #47 enhancements:
- Add thinking level syntax to --models (e.g., --models sonnet:high,haiku:low)
- First model in scope used as initial model when starting new session
- Auto-apply thinking level when cycling models with Ctrl+P
- Save both model and thinking to session AND settings for persistence
- Simplify UX by removing autoThinkingDisabled flag
- Fix model matching to prioritize exact matches over partial
- Support provider/modelId format (e.g., openrouter/openai/gpt-5.1-codex)

Issue #45:
- Add --thinking CLI flag to set thinking level directly
- Takes highest priority over all other thinking level sources

Closes #45

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

@@ -6,6 +6,7 @@ export interface Settings {
 	lastChangelogVersion?: string;
 	defaultProvider?: string;
 	defaultModel?: string;
+	defaultThinkingLevel?: "off" | "minimal" | "low" | "medium" | "high";
 	queueMode?: "all" | "one-at-a-time";
 	theme?: string;
 }
@@ -98,4 +99,13 @@ export class SettingsManager {
 		this.settings.theme = theme;
 		this.save();
 	}
+
+	getDefaultThinkingLevel(): "off" | "minimal" | "low" | "medium" | "high" | undefined {
+		return this.settings.defaultThinkingLevel;
+	}
+
+	setDefaultThinkingLevel(level: "off" | "minimal" | "low" | "medium" | "high"): void {
+		this.settings.defaultThinkingLevel = level;
+		this.save();
+	}
 }