build(scripts): add per-artifact build scripts staging into dist/

One script per main artifact, all staging into dist/ (overridable via
--dist or VOICECAT_DIST_DIR):

- build-server.sh        server-release preset -> dist/server/
- build-windows-client.sh  windows-client DLL + dotnet publish -> dist/windows-client/
- build-macos-client.sh    XCFramework + xcodebuild VoiceCatMac.app -> dist/macos-client/
- build-libs.sh           libvoicecat per platform -> dist/lib/{macos,ios*,windows}/
                         + dist/lib/VoiceCatCore.xcframework/
- build-all.sh            orchestrator (host-applicable artifacts only)
- common.sh               shared helpers: dist/VCPKG_ROOT resolution, platform
                         guards, logging, --help from header comments

Host-platform guards prevent running the wrong script on the wrong OS.
build-libs.sh and build-macos-client.sh drive the existing validated
clients/apple/scripts/build-xcframework.sh rather than duplicating it.
dist/ added to .gitignore.

scripts/build-windows-client.sh

@@ -0,0 +1,73 @@
+#!/usr/bin/env bash
+#
+# build-windows-client.sh — build the Windows WinForms client and stage a
+# runnable folder into dist/windows-client/.
+#
+# Two steps:
+#   1. Build the native voicecat.dll via the `windows-client` CMake preset
+#      (MinGW, static runtime — no libgcc_s_seh-1.dll / libstdc++-6.dll deps).
+#   2. `dotnet publish` the C# app (clients/windows/VoiceCat.App). The app's
+#      Directory.Build.props copies voicecat.dll into the output automatically.
+#
+# The staged folder contains VoiceCat.App.exe + voicecat.dll + all .NET deps,
+# ready to run. By default it is framework-dependent (needs the .NET 10 runtime
+# installed); pass --self-contained for a folder that runs without .NET.
+#
+# Usage:
+#   scripts/build-windows-client.sh                # build + stage into ./dist/windows-client
+#   scripts/build-windows-client.sh --dist /out
+#   scripts/build-windows-client.sh --no-configure # skip cmake configure (DLL step)
+#   scripts/build-windows-client.sh --self-contained
+#   scripts/build-windows-client.sh -h|--help
+#
+# Windows only (MSYS2/MinGW). Requires VCPKG_ROOT and the .NET 10 SDK.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+VC_SCRIPT_NAME="build-windows-client"
+source "$SCRIPT_DIR/common.sh"
+
+DO_CONFIGURE=true
+SELF_CONTAINED=false
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --dist)           vc_set_dist "$2"; shift 2 ;;
+        --no-configure)   DO_CONFIGURE=false; shift ;;
+        --self-contained) SELF_CONTAINED=true; shift ;;
+        -h|--help)        vc_print_help "$0"; exit 0 ;;
+        *) vc_die "unknown arg: $1 (try --help)" ;;
+    esac
+done
+
+vc_require_windows
+vc_log "dist dir: $VC_DIST_DIR"
+vc_resolve_vcpkg_root windows-client
+
+vc_step "build native DLL (preset: windows-client)"
+if $DO_CONFIGURE; then
+    cmake --preset windows-client
+fi
+cmake --build --preset windows-client
+DLL="$VC_REPO_ROOT/build/windows-client/bin/voicecat.dll"
+[[ -f "$DLL" ]] || vc_die "expected output not found: $DLL"
+vc_ok "voicecat.dll -> $DLL ($(vc_file_size "$DLL") bytes)"
+
+vc_step "publish C# app (dotnet publish)"
+APP_PROJ="$VC_REPO_ROOT/clients/windows/VoiceCat.App/VoiceCat.App.csproj"
+PUBLISH_DIR="$VC_REPO_ROOT/build/windows-client/publish"
+rm -rf "$PUBLISH_DIR"
+mkdir -p "$PUBLISH_DIR"
+
+PUBLISH_ARGS=(dotnet publish "$APP_PROJ" -c Release -o "$PUBLISH_DIR")
+if $SELF_CONTAINED; then
+    PUBLISH_ARGS+=( -r win-x64 --self-contained true )
+fi
+"${PUBLISH_ARGS[@]}"
+APP_EXE="$PUBLISH_DIR/VoiceCat.App.exe"
+[[ -f "$APP_EXE" ]] || vc_die "publish output missing VoiceCat.App.exe in $PUBLISH_DIR"
+
+vc_step "stage -> $VC_DIST_DIR/windows-client"
+STAGE="$(vc_dist_subdir windows-client)"
+cp -R "$PUBLISH_DIR/." "$STAGE/"
+vc_ok "VoiceCat.App.exe + deps -> $STAGE (voicecat.dll included)"
+vc_ok "done -> $STAGE"