feat(cartridge): Add echidna-llm VeriSimDB bridge adapter

V-lang adapter bridging echidna-llm tactic advisory to VeriSimDB for
persistent proof state storage. Routes through BoJ's verisimdb.zig FFI
with echidna-specific octad schema (8 modalities: semantic, temporal,
provenance, document, graph, vector, tensor, spatial).

Operations: store_proof, get_proof, find_similar, store_failure, stats.
Brings echidna-llm-mcp to 16 adapter files (15 protocols + VeriSimDB).

ECHIDNA Priority 3 (VeriSimDB integration) — BoJ side complete.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath