chore: scaffold aura workspace and wire the skills dev-cycle

Cargo workspace aura-core -> aura-engine -> aura-cli (bin `aura`) plus nodes/ for hot-reloadable cdylib node crates. Crate bodies are intentionally API-free; types arrive from the first spec. Adds the skills profile (.claude/dev-cycle-profile.yml), the project CLAUDE.md with the eight domain invariants, and the design-ledger skeleton.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/aura-core/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "aura-core"
+edition.workspace = true
+version.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[dependencies]