beads: add 6 spine finish-out beads for crate discovery, codegen, and integration

Tee up remaining work to get DSL-authored fingerprints (loan-tape.v1) working
end-to-end in run mode with real content extraction and BLAKE3 content hashes.

Ready (4 parallel):
- bd-28w: discover_installed() in registry/installed.rs
- bd-36b: extraction codegen wiring
- bd-1kv: publishable Cargo.toml dependency
- bd-3g1: trust config allowlist

Blocked:
- bd-1zj: content hash codegen (needs bd-36b)
- bd-2lg: spine integration validation (needs all 5)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: saltmachine