Context compaction: commands, auto-trigger, RPC support, /branch rework (fixes #92)

- Add compaction settings to Settings interface
- /compact [instructions]: manual compaction with optional focus
- /autocompact: toggle auto-compaction on/off
- Auto-compaction triggers after assistant message_end when threshold exceeded
- Footer shows (auto) when auto-compact is enabled
- RPC mode: {type: 'compact'} command emits CompactionEntry
- /branch now reads from session file to show ALL historical user messages
- createBranchedSessionFromEntries preserves compaction events

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

@@ -2,6 +2,12 @@ import { existsSync, mkdirSync, readFileSync, writeFileSync } from "fs";
 import { dirname, join } from "path";
 import { getAgentDir } from "./config.js";
 
+export interface CompactionSettings {
+	enabled?: boolean; // default: true
+	reserveTokens?: number; // default: 16384
+	keepRecentTokens?: number; // default: 20000
+}
+
 export interface Settings {
 	lastChangelogVersion?: string;
 	defaultProvider?: string;
@@ -9,6 +15,7 @@ export interface Settings {
 	defaultThinkingLevel?: "off" | "minimal" | "low" | "medium" | "high";
 	queueMode?: "all" | "one-at-a-time";
 	theme?: string;
+	compaction?: CompactionSettings;
 }
 
 export class SettingsManager {
@@ -108,4 +115,32 @@ export class SettingsManager {
 		this.settings.defaultThinkingLevel = level;
 		this.save();
 	}
+
+	getCompactionEnabled(): boolean {
+		return this.settings.compaction?.enabled ?? true;
+	}
+
+	setCompactionEnabled(enabled: boolean): void {
+		if (!this.settings.compaction) {
+			this.settings.compaction = {};
+		}
+		this.settings.compaction.enabled = enabled;
+		this.save();
+	}
+
+	getCompactionReserveTokens(): number {
+		return this.settings.compaction?.reserveTokens ?? 16384;
+	}
+
+	getCompactionKeepRecentTokens(): number {
+		return this.settings.compaction?.keepRecentTokens ?? 20000;
+	}
+
+	getCompactionSettings(): { enabled: boolean; reserveTokens: number; keepRecentTokens: number } {
+		return {
+			enabled: this.getCompactionEnabled(),
+			reserveTokens: this.getCompactionReserveTokens(),
+			keepRecentTokens: this.getCompactionKeepRecentTokens(),
+		};
+	}
 }