fix(cross-platform): remove bitcoinjs deep imports from internals

[landabaso]

• Reimplement required bitcoinjs internal helpers locally in src/bitcoinjs-lib-internals.ts (tapleafHash, tapTweakHash, witnessStackToScriptWitness, isTaprootInput) using public APIs and deterministic local serialization.
• Remove runtime deep import resolver logic to avoid bitcoinjs-lib/src/* dependency in bundled output.
• Update taproot control-block derivation in src/tapMiniscript.ts to use public payments.p2tr with scriptTree + redeem.
• Remove deep type import from src/tapMiniscript.ts by introducing local Taptree typing.
• Add test/bitcoinjsLibInternals.test.ts for behavior parity and a dist guard against reintroducing deep runtime imports.
• Remove stale comment in src/tapTree.ts and bump package version to 3.0.6.

Why

Node, CodeSandbox and React Native/Metro resolve modules differently; deep imports and dynamic require fallbacks are brittle across environments. This change moves internals access (imports from bitcoinjs-lib/src/) to a stable, public-API-based path while preserving behavior.