Bootstrap agent-ready docs and permissions (D-036)

Root AGENTS.md is now the single source of truth for coding agents;
CLAUDE.md, GEMINI.md and docs/CLAUDE.md are pointers. The product spec
moves from docs/CLAUDE.md to PRODUCT.md, DESIGN.md records the shipped
visual system, and docs/PERMISSIONS.md defines agent permission tiers
rendered to .claude/, .codex/ and .gemini/. Adds docs/specs/ and
docs/plans/, logs issues noticed (not fixed) in WorkBreakdown.md.

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

docs/specs/README.md

@@ -0,0 +1,11 @@
+# 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+- Front matter: `status: draft | approved | implemented | superseded`.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 — plans are
+  removed before merge.
+- Never delete an implemented spec; it is the record of intent.
+- A spec that makes an architectural choice also gets a `D-###` entry in `docs/Decisions.md`.