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/specs/README.md

@@ -0,0 +1,10 @@
+# Specs
+
+Approved specifications from the superpowers brainstorming workflow. Nothing non-trivial gets
+implemented without one.
+
+- Naming: `NNN-short-slug.md`, zero-padded, sequential.
+- A spec states **what** and **why**, plus acceptance criteria. Not **how**.
+- Front matter: `status: draft | approved | implemented | superseded`. No link to a plan, because plans are
+  removed before merge.
+- Never delete an implemented spec; it is the record of intent.