feat: agent and CLI control plane for sessions, worktrees, and scheduled tasks (#2408)

Add a shared OpenChamber control service with two thin adapters — a native
`openchamber` tool injected into managed OpenCode, and new CLI commands — so
users can manage parallel sessions, worktrees, and scheduled tasks
conversationally through agents or from the terminal.

Control plane:
- New openchamber-control service owning a fixed action contract:
  projects.list, models.list, session list/create/send/fork/status/messages,
  and schedule list/create/run/delete/toggle. Session and worktree deletion
  and project registration are deliberately not exposed.
- New openchamber-sessions module owning create/worktree/prompt orchestration,
  Goal Mode dispatch, wait semantics (initial idle never counts as completion;
  timeout and cancellation are failures), and explicit partial-failure results.
- Scheduled-task logic extracted into a service shared by routes, CLI, and the
  agent tool.

Agent tool:
- Managed OpenCode gets a materialized plugin registering one typed tool with
  a loopback-only callback, per-child ephemeral bearer (timing-safe, never
  persisted or logged), and abort propagation into the service.
- The ~1.5k-token schema applies progressive disclosure: short descriptions,
  server-side validation returning actionable usage errors, and intent
  guardrails — created sessions/tasks are user-facing work (not age
  self-delegation); worktree/goal/agent/variant/wait are omit-by-default;
  dispatches produce no completion notification, and later result r
  to session.messages, which now returns the authoritative sessionStatus.
- session.create without a user-named model picks from favorites/re
  send/fork omit the selection and the service reuses the target session's
  last user-message model, agent, and variant before falling back t
- An "Agent control tool" setting (default on, Save + Reload to apply)
  disables plugin injection entirely.

CLI:
- New `openchamber session`, `schedule`, `projects`, and `models` commands
  with automatic instance targeting, --wait/--timeout/--last-assist
  worktree flags, and Goal Mode, preserving interactive, non-TTY, --quiet,
  and --json contracts. The control HTTP timeout derives from the w
  instead of the 4-second default.

UI:
- New built-in "Schedule a Task" starter (/schedule-task) running a
  dialogue that defines a task and offers to create it via the tool after
  explicit confirmation; Craft a Goal and Feature Planning gain the
  handoff offer, and guided starters reserve the question tool for concrete
  option choices. Localized in all 10 locales, migrated into custom
  starter lists, hidden on VS Code.
- Sidebar shows CLI/agent-created sessions live via the control eve
- openchamber tool calls render with per-action titles and metadata.

packages/ui/src/lib/i18n/messages/ko.settings.ts

@@ -954,6 +954,9 @@ export const settingsDict = {
   'settings.openchamber.opencodeCli.field.binaryPathPlaceholder': '/Users/you/.bun/bin/opencode',
   'settings.openchamber.opencodeCli.field.showUpdateNotifications': 'OpenCode 업데이트 알림 표시',
   'settings.openchamber.opencodeCli.field.showUpdateNotificationsAria': 'OpenCode 업데이트 알림 표시',
+  'settings.openchamber.opencodeCli.field.agentControlTool': '에이전트 제어 도구',
+  'settings.openchamber.opencodeCli.field.agentControlToolAria': '에이전트 제어 도구 활성화',
+  'settings.openchamber.opencodeCli.field.agentControlToolInfo': '에이전트가 채팅에서 작업을 오케스트레이션할 수 있습니다. 세션과 worktree 생성, 다른 에이전트에게 프롬프트 위임, 예약 작업 관리가 가능합니다. 각 세션에 작은 도구 설명이 추가됩니다. Save + Reload 후 적용됩니다.',
   'settings.openchamber.opencodeCli.actions.browseAria': 'OpenCode binary 경로 찾아보기',
   'settings.openchamber.opencodeCli.actions.browse': '찾아보기',
   'settings.openchamber.opencodeCli.actions.saveAndReload': '저장 + 다시 로드',