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>

agents-docs/HANDOFF.md

@@ -0,0 +1,29 @@
+# Session Handoff
+
+> **New chat:** attach `@agents-docs/HANDOFF.md` (and only the files listed under Changed files). Say: continue from this handoff; do not redo completed work. Stay in default scope unless Next steps expand it.
+>
+> **Agents cannot open a new chat** — write/update this file, then ask the user to start one.
+
+**Status:** none
+
+<!-- When Status is `active`, fill every section below. When done with a handoff cycle, set Status back to `none` or overwrite on the next handoff. -->
+
+## Goal
+
+## Completed
+
+## Changed files
+
+## Decisions (this session only)
+
+## Failed approaches
+
+## Current issue / blockers
+
+## Next steps (exact)
+
+## Commands to continue
+
+## Scope note
+
+Default: `toju-app/` + targeted `electron/` + `.gitea/workflows/`. Out of scope unless listed here: `server/`, `e2e/`, `website/`, `docs-site/`.