fix(encode/windows): resolve NVENC at runtime — AMD/Intel hosts no longer crash at start

The nvenc build linked nvEncodeAPI64.dll's entry points at load time, so a
--features nvenc binary hard-crashed on any box without the NVIDIA driver
(AMD/Intel). Entry points now come from a runtime LoadLibrary table
(encode/windows/nvenc.rs load_api); a missing DLL just falls through the
encoder auto-detect to AMF/QSV/software. The generated import lib and all its
plumbing (gen-nvenc-importlib.ps1, nvenc.def, PUNKTFUNK_NVENC_LIB_DIR,
setup-build-env wiring) are gone.

Live-validated on the RTX 4090 box (NVENC session, 7000+ frames).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packaging/windows/nvenc/gen-nvenc-importlib.ps1

@@ -1,57 +0,0 @@
-<#
-.SYNOPSIS
-  Generate the NVENC import library (nvencodeapi.lib) into -OutDir, so the host links with
-  `--features nvenc` on a box that has no NVIDIA Video Codec SDK and no GPU.
-
-.DESCRIPTION
-  The host links against nvencodeapi.lib (crates/punktfunk-host/build.rs). That import lib is just
-  a link-time stub for two exports of nvEncodeAPI64.dll (the real DLL ships with the NVIDIA driver
-  and resolves at runtime). We synthesise it from nvenc.def:
-
-    1. llvm-dlltool  — preferred; LLVM is on the CI runner PATH (C:\Program Files\LLVM\bin) and this
-                       works without a Visual Studio developer shell.
-    2. MSVC lib.exe  — fallback; located via vswhere (no vcvars needed).
-
-  Point PUNKTFUNK_NVENC_LIB_DIR at -OutDir before `cargo build --features nvenc`.
-
-.EXAMPLE
-  pwsh -File gen-nvenc-importlib.ps1 -OutDir C:\t\nvenc
-#>
-[CmdletBinding()]
-param(
-    [Parameter(Mandatory = $true)][string]$OutDir,
-    [string]$DefPath = (Join-Path $PSScriptRoot 'nvenc.def')
-)
-$ErrorActionPreference = 'Stop'
-$ProgressPreference = 'SilentlyContinue'
-$PSNativeCommandUseErrorActionPreference = $false   # check $LASTEXITCODE ourselves (pwsh 7.4 safe)
-
-if (-not (Test-Path $DefPath)) { throw "module-definition file not found: $DefPath" }
-New-Item -ItemType Directory -Force -Path $OutDir | Out-Null
-$out = Join-Path $OutDir 'nvencodeapi.lib'
-
-# 1) llvm-dlltool (preferred) ------------------------------------------------------------------
-$dlltool = Get-Command llvm-dlltool -ErrorAction SilentlyContinue
-if ($dlltool) {
-    Write-Host "==> llvm-dlltool -> $out"
-    & $dlltool.Source -m i386:x86-64 -d $DefPath -D nvEncodeAPI64.dll -l $out
-    if ($LASTEXITCODE -ne 0) { throw "llvm-dlltool failed ($LASTEXITCODE)" }
-    Write-Host "    ok ($((Get-Item $out).Length) bytes)"
-    return
-}
-
-# 2) MSVC lib.exe via vswhere (fallback) -------------------------------------------------------
-$vswhere = Join-Path ${env:ProgramFiles(x86)} 'Microsoft Visual Studio\Installer\vswhere.exe'
-if (Test-Path $vswhere) {
-    $lib = & $vswhere -latest -prerelease -products * -find 'VC\Tools\MSVC\**\bin\Hostx64\x64\lib.exe' |
-        Select-Object -First 1
-    if ($lib -and (Test-Path $lib)) {
-        Write-Host "==> lib.exe -> $out"
-        & $lib "/def:$DefPath" /machine:x64 "/out:$out"
-        if ($LASTEXITCODE -ne 0) { throw "lib.exe failed ($LASTEXITCODE)" }
-        Write-Host "    ok ($((Get-Item $out).Length) bytes)"
-        return
-    }
-}
-
-throw "neither llvm-dlltool (LLVM bin on PATH) nor MSVC lib.exe (via vswhere) was found to build $out"

packaging/windows/nvenc/nvenc.def

@@ -1,14 +0,0 @@
-; Module-definition file for the NVENC import library the host links against with `--features nvenc`.
-;
-; The real entry points live in nvEncodeAPI64.dll, which ships with the NVIDIA driver. At LINK time
-; the host only needs an import library exporting these two symbols (see crates/punktfunk-host/build.rs:
-; it emits `cargo:rustc-link-lib=dylib=nvencodeapi` and searches PUNKTFUNK_NVENC_LIB_DIR). No GPU,
-; driver, or NVIDIA Video Codec SDK is required to BUILD — only to run, where the DLL resolves from
-; the installed driver. Generate nvencodeapi.lib from this file with gen-nvenc-importlib.ps1.
-;
-; The LIBRARY line names the DLL the import records point at — required for MSVC `lib.exe /def`
-; (without it the import name would default to "nvenc.dll"). llvm-dlltool takes the name from `-D`.
-LIBRARY nvEncodeAPI64.dll
-EXPORTS
-    NvEncodeAPICreateInstance
-    NvEncodeAPIGetMaxSupportedVersion