Remove Hardhat completely

[clement-ux]

Stack

• Base: Replace Hardhat ops runtime and local fork with standalone CLI and Anvil #2994
• This PR: remove the previous runtime completely

Merge order: this PR into #2994, then #2994 into #2993. Do not merge directly to master.

Summary

• remove the old runtime config, node wrapper, helper files, and npm packages
• replace the temporary registration shim with a local task / subtask registry
• remove fallback RPC namespaces; Anvil is the only local node API
• rename signer and descriptor tooling to runtime-neutral names
• update active docs, runlogs, fixtures, skills, and comments
• remove the stale Slither finding for the deleted dependency console

Invariants

• all 75 public ops commands remain in the catalogue
• all 74 registry-backed commands have live handlers; accounts remains a direct standalone command
• mainnet forks stay distinct from live mainnet via FORK=true
• git grep -in hardhat returns zero matches
• no tracked filename contains the removed runtime name

Verification

• pnpm install --frozen-lockfile
• pnpm test:tasks (39 passing)
• pnpm test:brownie (4 passing)
• pnpm test:anvil (2 passing)
• pnpm test:scripts (66 passing)
• pnpm test:layouts (5 passing)
• pnpm typecheck
• pnpm lint:js
• pnpm lint:ts
• pnpm prettier:check
• forge fmt --check on all touched Solidity files
• forge build contracts/ -j 1
• pnpm ops help
• independent pre-commit review: PASS, no high/medium blockers