feat: remote-control live DSH Web sessions from Telegram

Attach via /sessions picker instead of creating parallel agents; mirror the same session trajectory to phone and Web (Codex-style remote).

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/DESIGN.md

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+# Design: Telegram remote control for live DSH sessions
+
+Date: 2026-08-14  
+Status: Approved (ship MVP)
+
+## Goal
+
+Phone Telegram remote-controls **live** DeepSeek Harness agents in the same `dsh web` process (Codex-style). Web session is source of truth; Telegram attaches — does **not** create parallel agents.
+
+## MVP
+
+- Auth allowlist + long poll
+- `/sessions` lists `ctx.agents.list()` / `roots()` with inline keyboard
+- Bind chat → live `Agent`; plain text → `agent.followup`
+- Mirror `session/event` (`turn/start`, `assistant/message`) to all Telegram chats bound to that session id
+- `/unbind` clears binding only (never dispose host agent)
+- Empty live list → prompt to open a Web conversation first
+
+## Non-goals (later)
+
+- Disk resume / history search
+- Auto-create parallel agents
+- Streaming edit-in-place, media, webhook
+
+## Binding rules
+
+- One Telegram chat → at most one bound agent; re-select replaces
+- Multiple chats may bind the same live agent (all receive mirrors)
+- On `stop()`: clear bindings only; do not dispose live agents