mom: refactor to use AgentSession for context management

- Export AgentSession, SessionManager, SettingsManager, compaction from coding-agent
- Create MomSessionManager for channel-based context.jsonl storage
- Create MomSettingsManager for mom-specific settings
- Refactor agent.ts to use AgentSession instead of ephemeral Agent
- Split logging: tool results go to context.jsonl, human messages to log.jsonl
- Enable auto-compaction and overflow detection from coding-agent

Part of #115

packages/coding-agent/src/index.ts

@@ -1,3 +1,27 @@
+// Core session management
+export {
+	AgentSession,
+	type AgentSessionConfig,
+	type AgentSessionEvent,
+	type AgentSessionEventListener,
+	type CompactionResult,
+	type ModelCycleResult,
+	type PromptOptions,
+	type SessionStats,
+} from "./core/agent-session.js";
+// Compaction
+export {
+	type CutPointResult,
+	calculateContextTokens,
+	compact,
+	DEFAULT_COMPACTION_SETTINGS,
+	estimateTokens,
+	findCutPoint,
+	findTurnStartIndex,
+	generateSummary,
+	getLastAssistantUsage,
+	shouldCompact,
+} from "./core/compaction.js";
 // Hook system types
 export type {
 	AgentEndEvent,
@@ -18,6 +42,32 @@ export type {
 	TurnEndEvent,
 	TurnStartEvent,
 } from "./core/hooks/index.js";
-export { SessionManager } from "./core/session-manager.js";
+export { messageTransformer } from "./core/messages.js";
+export {
+	type CompactionEntry,
+	createSummaryMessage,
+	getLatestCompactionEntry,
+	type LoadedSession,
+	loadSessionFromEntries,
+	type ModelChangeEntry,
+	parseSessionEntries,
+	type SessionEntry,
+	type SessionHeader,
+	SessionManager,
+	type SessionMessageEntry,
+	SUMMARY_PREFIX,
+	SUMMARY_SUFFIX,
+	type ThinkingLevelChangeEntry,
+} from "./core/session-manager.js";
+export {
+	type CompactionSettings,
+	type RetrySettings,
+	type Settings,
+	SettingsManager,
+} from "./core/settings-manager.js";
+
+// Tools
 export { bashTool, codingTools, editTool, readTool, writeTool } from "./core/tools/index.js";
+
+// Main entry point
 export { main } from "./main.js";