feat: restore account modules and verification coverage

[leekt]

Summary

• restore dropped account actions, hooks, policies, P256/WebAuthn signers, and validators
• add shared weighted-threshold validation and a native multi-owner validator
• add behavior-tree coverage plus Certora, Halmos, and Kontrol verification assets
• migrate WebAuthn verification to Solady while preserving the existing six-field signature ABI

Impact

This expands the ERC-7579 module set, strengthens weighted-signature validation, and removes the repository's custom WebAuthn/P256/Base64URL implementation in favor of the pinned Solady library. The legacy usePrecompiled signature field remains ABI-compatible, while Solady now selects the available P256 verifier automatically.

Validation

• forge build
• forge test — 716 passed, 0 failed
• WebAuthn Halmos safety proofs — 15 passed, 0 failed
• WebAuthn Halmos non-vacuity witnesses — all 8 produced expected counterexamples
• git diff --check