Biome noParameterProperties: never use TypeScript constructor parameter properties in class definitions

Trap: TypeScript parameter properties (constructor(private readonly handle: FileHandle)) look like idiomatic shorthand and compile fine. But Biome enforces noParameterProperties and will error. Fix: always declare explicit class fields and assign in constructor body. Applies to all new classes in src/lib/**/*.ts. Caught during FileOldReader/MemoryOldReader addition in bspatch.ts — 4 Biome errors at lines 281, 310, 311, 312.