SKALE L2 Anchoring Support

[MoltyCel]

Summary

Add SKALE Network as a supported anchoring chain alongside Base L2. MolTrust's anchor format is chain-agnostic by design (TechSpec v0.8 §6.4); this issue tracks the concrete steps to enable SKALE support.

Why SKALE

SKALE satisfies all three requirements from TechSpec §6.4:

• Transaction finality under 10 seconds ✓ (single-block finality)
• Permanent data availability ✓
• Public block explorer ✓

Additional benefit: zero gas fees (sFUEL model).

Technical Scope

1. Chain config update

CHAIN_CONFIG = {
    "base": {"rpc": "https://mainnet.base.org", "chain_id": 8453},
    "skale": {"rpc": "https://mainnet.skalenodes.com/v1/<chain>", "chain_id": "TBD"}
}

2. Anchor format (unchanged)

MolTrust/DocumentIntegrity/1 SHA256:<hash> — same calldata prefix, chain-agnostic.

3. Verification endpoint update

Accept chain parameter in /provenance/verify to look up anchors on the correct explorer.

4. sFUEL distribution

Set up sFUEL faucet or distribution for the operator wallet.

Acceptance Criteria

• SKALE chain config added
• Anchor transaction succeeds on SKALE testnet
• Verification endpoint resolves SKALE anchors
• Documentation updated (TechSpec appendix)
• Integration test passes