feat(solana): add list_solana_validators ranking helper (#436)

[szhygulin]

Summary

Adds a read-only list_solana_validators tool — the Solana parallel to list_tron_witnesses — so agents can surface a ranked menu before calling prepare_native_stake_delegate instead of forcing the user to leave for stakewiz / validators.app and paste back a vote pubkey. Smoke-test script 040 was the trigger.

Closes #436.

What changes

• New module src/modules/solana/validators.ts (~250 LoC + zod schema + types).
  • Wraps the stakewiz.com public feed (https://api.stakewiz.com/validators, no API key required).
  • Filters: commissionMaxPct, excludeDelinquent (default true), excludeSuperminority (default false), minActivatedStakeSol, mevEnabled.
  • Sort: score (default — wiz_score desc), apy, stake, commission.
  • Default limit 25, max 100.
• Tool registration in src/index.ts next to prepare_native_stake_delegate. Cross-references the new tool from the delegate description ("To pick a validator, call list_solana_validators first").
• Scope gating: src/config/scope.ts adds explicit name === "list_solana_validators" to the Solana family block; matching test/scope.test.ts row.
• 14 new unit tests in test/list-solana-validators.test.ts covering filters, sorts, limit, fetch failure, and Inv Add Base network support (chainId 8453) #14 notes.

Why stakewiz, not validators.app

• validators.app requires a per-user API token; stakewiz is open.
• stakewiz exposes both total_apy (inflation + MEV) AND the composite wiz_score, covering all four sortBy modes directly.

Invariant #14 awareness

The vote pubkey is a "durable on-chain object selected from a multi-candidate set" — exactly the b040 attack class Inv #14 (#460) defends against. This tool is a HELPER, not a source-of-truth replacement. A compromised MCP could swap the list. Two concrete defenses are baked in:

1. Per-validator stakewizUrl in every row — the user pastes it into a browser to re-verify activated stake / commission / delinquent status against an authority outside the MCP enumeration.
2. notes[] array on every response surfaces verbatim Inv Add Base network support (chainId 8453) #14 instructions: re-verify on stakewiz.com / validators.app, then byte-equality-check the votePubkey in the prepare_native_stake_delegate response against the one confirmed in step 1.

The tool description in src/index.ts also references Invariant #14 explicitly so agents pass the gate through to the user.

Caching

CACHE_TTL.YIELD (600s / 10 min). Validator rankings don't change rapidly between epochs (~2 days each); 10-min staleness is acceptable for a "where should I delegate" comparison and amortizes the ~1.5MB feed payload.

Test plan

• npm run build clean
• npx tsc --noEmit clean
• npx vitest run — all 2382 tests pass locally (14 new + 2368 prior)
• CI green
• Manual: list_solana_validators({}) returns top-25 by wiz_score
• Manual: list_solana_validators({sortBy:"apy", filters:{mevEnabled:true, commissionMaxPct:5}, limit:10}) returns top-10 Jito-enabled, commission≤5% validators by APY
• Manual: feed unreachable (e.g. block stakewiz.com via /etc/hosts) → empty validators[] + clear unreachable note

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