feat: khipu standalone — notas P2P soberanas content-addressed, local-first (front-door, git-dep al monorepo)

Front-door limpio: solo crates del dominio; Llimphi y lo fundacional por
git-dep del monorepo gioser.git. cargo check pasa (5 crates, 0 errores).

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

README.md

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+# khipu
+
+> Sovereign P2P "notes to oblivion" — local-first, content-addressed, in Rust.
+
+`khipu` (Quechua: *knotted-cord record*) is a sovereign note system: local-first, content-addressed, synced peer-to-peer over the `card`/`chasqui` layer (LAN + WAN + relay/NAT traversal, UDP & DHT discovery, encrypted identity). Notes are designed to be let go of as much as kept — a record that forgets on purpose.
+
+## How dependencies work
+Front-door repo: only `khipu-*` crates here. Identity (`card`), networking (`chasqui`) and shared leaves are git-dependencies of the [`gioser`](https://gitea.gioser.net/sergio/gioser) monorepo.
+
+## License
+MIT. Part of the [gioser](https://gitea.gioser.net/sergio/gioser) suite.