feat: PyVNCServer 3.3 — native DXGI metadata and encoding interoperability

[xulek]

PyVNCServer 3.3 — DXGI metadata + interoperability

This PR implements the v3.3 capture/interoperability milestone.

Native DXGI metadata

• reads IDXGIOutputDuplication::GetFrameDirtyRects and GetFrameMoveRects while the DXCam frame is still acquired
• reuses DXCam's existing Desktop Duplication object instead of starting a second capture stack
• validates and clips native dirty/move rectangles before exposing them to the framebuffer pipeline
• treats a successful DXGI no-new-frame result as an authoritative empty update
• falls back to the existing software framebuffer differ whenever native metadata cannot be read or validated safely
• automatically disables native metadata for scaled, rotated or cropped DXCam captures until coordinate translation is implemented
• exposes DXGI move rectangles as CopyRect hints
• conservatively includes move destinations in dirty pixel regions as well, preserving correctness for clients without CopyRect and clients that skip producer generations

UltraVNC / encoding interoperability

Adds real TCP/RFB end-to-end regressions that keep one connection open while changing the client's advertised encoding set.

The CI matrix parses the actual wire payload for:

Raw → RRE → Hextile → Zlib → ZRLE → Tight → Raw

There is also an explicit RRE → Tight regression matching the failure mode previously observed with UltraVNC. These tests validate both the rectangle encoding ID and the corresponding payload framing/decoding.

DXCam contract protection

• performance extra now requires dxcam>=0.3.0
• a dedicated Windows CI job installs .[dev,performance]
• the job verifies the actual DXCam private integration points and the Desktop Duplication dirty/move methods
• the ctypes/COM vtable path is exercised by a synthetic ABI test without requiring an interactive desktop

Diagnostics and docs

• adds benchmarks/benchmark_dxgi_metadata.py
• documents native metadata, fallback semantics and conservative move handling
• documents the automated and manual UltraVNC compatibility matrix
• bumps package version to 3.3.0

Run the real Windows diagnostic with:

python -m pip install -e ".[performance]"
python benchmarks/benchmark_dxgi_metadata.py --frames 300 --fps 60

Validation

Current GitHub Actions result is fully green:

• Ubuntu / Python 3.11: ✅
• Ubuntu / Python 3.12: ✅
• Ubuntu / Python 3.13: ✅
• Windows / Python 3.13: ✅
• Windows DXCam [performance] contract: ✅
• coverage: ✅
• wheel + sdist build: ✅
• distribution validation + wheel install smoke test: ✅

Remaining manual validation before release

A GitHub-hosted Windows runner can validate the DXCam ABI but cannot provide a representative interactive desktop/GPU capture workload. Before merging/releasing v3.3, run the DXGI metadata benchmark and an UltraVNC session on a real Windows desktop, especially window movement, scrolling, Tight and RRE switching.