chore: cut agent token burn with scoped bootstrap and handoffs

Slim always-on agent docs, default to toju-app plus targeted electron, and add HANDOFF.md plus a Cursor rule so long chats reset cleanly without agents opening new chats.

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

.cursor/rules/handoff.mdc

@@ -0,0 +1,24 @@
+---
+description: Short-chat handoff to cut token burn; agents cannot open new chats
+alwaysApply: true
+---
+
+# Handoff (token control)
+
+Agents **cannot** create a new Cursor chat. When a handoff is needed, write `agents-docs/HANDOFF.md` and tell the user to start a **new chat** with `@agents-docs/HANDOFF.md`.
+
+## When to hand off
+
+- User says "handoff", "new chat", or "wrap up this session"
+- Thread is long (many tool rounds, large pastes, repeated failed approaches) and more major work remains
+- Switching to a clearly separate objective
+
+## What to do
+
+1. Overwrite `agents-docs/HANDOFF.md` — set `Status: active`; fill Goal, Completed, Changed files, Decisions, Failed approaches, Current issue, Next steps, Commands.
+2. Stop major new work in this chat after writing the handoff (unless the user says continue here).
+3. Tell the user the one-liner to paste in the new chat.
+
+## New-chat bootstrap
+
+If `agents-docs/HANDOFF.md` has `Status: active`, read it first and continue Next steps. Do not reload the whole monorepo or redo Completed work.