chore: bootstrap agent-ready docs, rules and Bun workspace

Adds the approved v1 design spec, UI mockups, AGENTS.md (with CLAUDE.md
and GEMINI.md pointers), architecture/decisions/todo/permissions docs,
agent permission files, and an empty Bun workspaces skeleton.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/plans/README.md

@@ -0,0 +1,11 @@
+# Plans
+
+Implementation plans from the superpowers writing-plans workflow. **Transient:** a plan lives only on
+its feature branch and is removed with `git rm` before the merge request is opened. This README stays.
+
+- Naming: `NNN-short-slug.md`, matching its spec number.
+- Each plan links back to its spec and has bite-sized checkbox tasks with exact file paths, test commands, and
+  commit checkpoints.
+- Write it for an engineer with zero context for this codebase. Spell out the obvious.
+- Tick checkboxes as you go so another agent can resume an interrupted session.
+- Front matter: `status: draft | approved | in-progress`. There is no `done`, because a finished plan is deleted.