add vault first time control

src/utils/sss.ts

@@ -1,11 +1,16 @@
 /**
  * Shamir's Secret Sharing (SSS) Implementation
- * 
+ *
  * This implements a (3,2) threshold scheme where:
  * - Secret is split into 3 shares
  * - Any 2 shares can recover the original secret
- * 
- * Based on the Sentinel crypto_core_demo Python implementation.
+ *
+ * Correspondence with crypto_core_demo (Python):
+ * - sp_trust_sharding.py: split_to_shares(), recover_from_shares()
+ * - Same algorithm: f(x) = secret + a*x (mod P), Lagrange interpolation
+ * - Difference: entropy conversion. Python uses BIP-39 (mnemonic.to_entropy);
+ *   we use custom word list index-based encoding for compatibility with
+ *   existing MNEMONIC_WORDS. SSS split/recover logic is identical.
  */
 
 // Use a large prime for the finite field