feat: conversation compacting (manual + automatic)

Implement roadmap item 10: conversation compaction to reclaim context
window without losing the thread.

Wire (0.11.0):
- Add CompactionResult type
- Add ConversationCompactedMessage WS event

Transport-contract (0.15.0):
- Add CompactResponse, CompactThresholdResponse, SetCompactThresholdRequest
- Add ConversationCompactedMessage to WsServerMessage union
- Re-export CompactionResult

Conversation-store:
- replaceHistory: delete all chunks, reset seq, append new messages
- getCompactThreshold / setCompactThreshold (per-conversation setting)
- compactThresholdKey added to keys.ts

Session-orchestrator:
- CompactionService interface + compactionHandle
- conversationCompacted hook descriptor
- createCompactionService: load history, split old/recent, call provider
  to summarize, replaceHistory with [system: summary] + recent N
- Auto-trigger: resolveCompaction lazy dep, fires after turn settles
  (checks threshold, non-blocking)
- Hook declared in manifest contributes.hooks + services

Transport-http:
- POST /conversations/:id/compact (manual trigger)
- GET /conversations/:id/compact-threshold (read setting)
- PUT /conversations/:id/compact-threshold (set setting)

Transport-ws:
- Subscribe to conversationCompacted hook
- Broadcast conversation.compacted WS message

CLI:
- dispatch compact <conversationId> command

FE handoff: frontend-compaction-handoff.md

1 files changed, 20 insertions, 0 deletions

diff --git a/packages/cli/src/main.ts b/packages/cli/src/main.ts
index e709f21..4e07da9 100644
--- a/packages/cli/src/main.ts
+++ b/packages/cli/src/main.ts
@@ -9,6 +9,7 @@ import { readFile } from "node:fs/promises";
 import { parseArgs } from "./args.js";
 import { formatCatalog } from "./catalog.js";
 import {
+	compactConversation,
 	enqueueMessage,
 	fetchConversations,
 	fetchLastMessage,
@@ -23,6 +24,7 @@ import { extractLastText, formatConversationList, renderEvent } from "./render.j
 const USAGE = `Usage:
   dispatch models [--server <url>]
   dispatch list [<prefix>] [--status <active|idle|closed>] [--all] [--server <url>]
+  dispatch compact <conversationId> [--server <url>]
   dispatch read <conversationId> [--server <url>]
   dispatch open <conversationId> [--server <url>]
   dispatch send <conversationId> --text "..." [--queue] [--open] [--cwd <dir>] [--effort <level>] [--server <url>]
@@ -79,6 +81,24 @@ async function main(): Promise<void> {
 			if (last.content.length > 0) process.stdout.write(`${last.content}\n`);
 			break;
 		}
+		case "compact": {
+			const resolved = await resolveConversationId(
+				{ fetchImpl: globalThis.fetch },
+				{ server: parsed.server, shortId: parsed.conversationId },
+			);
+			if (typeof resolved !== "string") {
+				process.stderr.write(`${resolved.error}\n`);
+				process.exit(1);
+			}
+			const result = await compactConversation(
+				{ fetchImpl: globalThis.fetch },
+				{ server: parsed.server, conversationId: resolved },
+			);
+			process.stdout.write(
+				`Compacted ${resolved}: ${result.messagesSummarized} messages summarized, ${result.messagesKept} kept.\n`,
+			);
+			break;
+		}
 		case "open": {
 			const resolved = await resolveConversationId(
 				{ fetchImpl: globalThis.fetch },