v1.11: opencode-style compaction port

- compaction.ts: usable/isOverflow/estimate/turns/select/buildPrompt/process
- compaction-prompt.ts: SUMMARY_TEMPLATE verbatim from opencode
- schema: messages.{compacted_at,summary,tail_start_id} + chats.needs_compaction
- inference: auto-trigger on overflow, pre-fetch compaction before next turn
- /compact slash command rewired to new path
- WS: chat_status working/idle around compaction + compacted frame
- frontend: SummaryCard + sonner toast on compacted
- 24 unit tests for pure functions

apps/server/src/routes/chats.ts

@@ -316,7 +316,8 @@ export function registerChatRoutes(
       }
       const rows = await sql<Message[]>`
         SELECT id, session_id, chat_id, role, content, kind, tool_calls, tool_results, status, last_seq,
-               tokens_used, ctx_used, ctx_max, started_at, finished_at, created_at, metadata
+               tokens_used, ctx_used, ctx_max, started_at, finished_at, created_at, metadata,
+               summary, tail_start_id, compacted_at
         FROM messages
         WHERE chat_id = ${req.params.id}
         ORDER BY created_at ASC, id ASC