Improvements

[pro100andrey]

BREAKING CHANGES:

• BinaryWriterPool: renamed _defaultBufferSize → _initialBufferSizer (and parameter defaultBufferSize → initialBufferSizer in acquire() and withWriter())

New Features:

• BinaryWriterPool: added _discardedPoolFull counter — tracks writers discarded due to pool full (max 32)
• BinaryWriter: added _varIntSize(int value) — helper function for VarInt size calculation (switch expression)
• BinaryReader: added peekByte() — returns byte at current position without advancing offset
• BinaryReader: added BinaryReader.fromList(List<int>) — convenient constructor for List<int>

Fixes:

• BinaryWriterPool: added validation for initialBufferSizer in acquire() — throws RangeError for invalid size
• BinaryWriterPool: _initializeBuffer() now resets _isInPool = false, correct takeBytes() → release() flow for pooled writers
• BinaryWriterPool: clear() now resets _isInPool for pooled writers
• BinaryReader/BinaryWriter: removed unnecessary late from _ReaderState and _WriterState (offset, capacity, list)
• BinaryReader: removed redundant bounds check in peekBytes() (already guarded by _checkBounds)

Refactoring:

• _WriterState: renamed _validated → _fromSize
• string_utils.dart: replaced JSDoc tags @param/@return with Dart style (Parameters:/Returns:)

Tests:

• Added tests for pool statistics, edge cases takeBytes/reset/release