Optimize NIF parsing: reduce allocations, fix cross-platform builds

[Copilot]

Identified and fixed performance bottlenecks and platform compatibility issues in NIF file parsing.

Build Fixes

• Cross-platform NIFORGE_API macro (added GCC __attribute__((visibility)) for non-Windows)
• Removed #pragma once from .cpp file
• Added missing <cmath>, <cstring> includes

Performance Optimizations

String handling - Eliminated allocations in hot paths:

// Before: creates temporary string on every block
std::string blockType = getReadableText(header.blockTypes[...]);
auto it = factories.find(blockType);

// After: zero-copy view
std::string_view blockType = getReadableText(header.blockTypes[...]);
auto it = factories.find(blockType);  // map now uses string_view keys

Vector operations:

• Pre-allocated blocks.reserve(header.numBlocks) before parsing loop
• emplace_back() instead of push_back() for 10+ constructor calls (NiNode, NiMesh, NiHeader, etc.)
• Fixed bug: NiHeader used capacity() in loop condition instead of actual count

Type correctness:

• Loop indices now use proper unsigned types (uint16_t, uint32_t) matching NIF spec
• Replaced dynamic_pointer_cast with direct dynamic_cast in parseDataStreams

Move semantics - Added noexcept to move ops (NiFile, NiDataStream) for container optimization

Const correctness - getBlocksOfType() and getRootNodes() now const-qualified

Example Impact

Factory lookup no longer allocates/copies strings for each of the ~100 blocks in a typical NIF file. Vector reservations eliminate 3-4 reallocations per parsing pass.

Original prompt

Identify and suggest improvements to slow or inefficient code

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