GUI rework for source-only builds + CLI security fixes + packaging + cross-platform scaffolding

Fixes the "GUI functions don't work on GNU Guix" report and a batch of
adversarial-audit findings across the CLI, decoder, crypto and packaging.

GUI (gui/src/zupt_gui.py)
- Root cause of the broken GUI: every encryption path defaulted to the
  libzuptsdk "SDK v2" modes, which are absent from the source-only build and
  exit 1. Reworked Keys/Compress/Extract around the native modes with a
  build-aware PQ-mode selector: Hybrid (--pq, default), Full PQ (--pq-only),
  and SDK v2 only when the binary reports WITH_SDK support. Capability is
  detected from `version` ("Build:"/"KDF:" lines) with a `help` fallback.
- Extract/Verify gain a PQ private-key input with auto-detect (reads the
  archive via `info` to pick --pq vs --pq-only). Verify could not verify any
  PQ archive before (password field only).
- run_async now holds a LIST of in-flight (thread, worker) refs; DiskTab's two
  buttons previously shared one slot, so a second op GC'd the first QThread
  mid-run. About tab corrected (codec 2.60.4, PBKDF2 default, --pq-only, URL).

CLI (src/zupt_main.c)
- compress -p <archive> <files> swallowed the archive name as the password and
  truncated the first input file (silent data loss, exit 0). Added a
  data-loss guard: refuse to overwrite an existing non-.zupt file as the output
  archive unless -y/--force; plus a self-overwrite guard.
- compress <archive> <src> -p <pw> wrote an UNENCRYPTED archive (exit 0)
  because options after the first positional were treated as files. Now errors
  on a misplaced option (with a `--` escape for real dashed filenames).
- Removed duplicated dead --pq-box/--pq-sdk branches. version/banner/usage now
  state the build's real KDF (PBKDF2 on source-only) and repo URL; examples
  lead with native --pq / --pq-only.

Security (audit findings)
- vv_decoder.c: the two AVX2 fast-path token decoders read a 2-/3-byte match
  offset after only checking 1 byte remained -> heap over-read on a crafted
  archive. Added the `ip + off_bytes > ip_end` guard the tail path already had.
- zupt_crypto.c: wipe ML-KEM/X25519 secret-key buffers when hybrid decrypt
  init fails on key read (matches the pq-only path).
- zupt_format.c: bound attacker-controlled encryption_header_off before the
  (off_t)+7 arithmetic in the info enc_type reader (avoid signed-overflow UB).

Packaging (would fail source-only)
- debian/rules (staged into debian/zupt, installed vendored .so), aur/PKGBUILD,
  nix/flake.nix, homebrew (vendored .so + nonexistent AUDIT.md, stale /zupt
  URLs) now build source-only. opensuse spec %files ships the shell completions
  make install writes (rpmbuild no longer fails on unpackaged files);
  _service + debian/control point at the vaptvupt repo; KDF claim corrected.

Cross-platform GUI packaging (new)
- packaging/portable/: OS-agnostic GUI package (zupt_gui.py + .bat/.command/.sh
  launchers + README) that runs on Windows/macOS/Linux/BSD with Python+PySide6.
- .github/workflows/cross-platform.yml: builds real native binaries on
  windows-latest + macos-latest runners (CLI, PyInstaller GUI, Inno Setup
  installer, .dmg) and the portable zip, attaching them to the release on tag.
- packaging/windows/vaptvupt-gui.iss: Inno Setup installer script.

Validation: make check 16/16 (all distro-safe checks), GUI imports + command
contracts verified against the fixed CLI. test_help_consistency updated to
assert the truthful (build-aware) default KDF.

packaging/aur/PKGBUILD

@@ -18,7 +18,7 @@ replaces=('zupt')
 conflicts=('zupt')
 pkgdesc='Pure-C11 post-quantum backup compression utility (AES-256-CTR + HMAC-SHA256 + ML-KEM-768 + X25519)'
 arch=('x86_64' 'aarch64')
-url='https://git.securityops.co/cristiancmoises/zupt'
+url='https://git.securityops.co/cristiancmoises/vaptvupt'
 license=('AGPL-3.0-or-later')
 depends=('glibc')
 makedepends=('gcc')
@@ -26,39 +26,31 @@ checkdepends=('python')
 
 # Replace SHA256 placeholder with output of:
 #   sha256sum /tmp/zupt-2.4.4.tar.gz
-source=("${pkgname}-${pkgver}.tar.gz::https://git.securityops.co/cristiancmoises/zupt/releases/download/v${pkgver}/${pkgname}-${pkgver}.tar.gz")
+source=("${pkgname}-${pkgver}.tar.gz::https://git.securityops.co/cristiancmoises/vaptvupt/releases/download/v${pkgver}/${pkgname}-${pkgver}.tar.gz")
 sha256sums=('SKIP')
 
 build() {
     cd "${pkgname}-${pkgver}"
-    # Strict-warning build that the project's own §6 verification matrix uses.
+    # Source-only build (WITH_SDK=0) with the project's strict warning set.
     CFLAGS="${CFLAGS:--O2 -std=c11} -Wall -Wextra -Wpedantic" \
-        make -j"$(nproc)"
+        make WITH_SDK=0 -j"$(nproc)"
 }
 
 check() {
     cd "${pkgname}-${pkgver}"
-    # Project regression suite — F-06 HMAC, F-08 top-MAC, F-09 byte sweep, etc.
-    make test
+    # Distro-safe regression subset (F-06..F-12, dedup-nonce, NIST/RFC vectors).
+    make WITH_SDK=0 check
 }
 
 package() {
     cd "${pkgname}-${pkgver}"
-    make DESTDIR="${pkgdir}" PREFIX=/usr install
+    # Source-only build (no vendored libraries); `make install` places the
+    # binary, the zupt symlink, the man pages and the shell completions.
+    make DESTDIR="${pkgdir}" PREFIX=/usr WITH_SDK=0 install
 
     # Docs that aren't part of `make install`
-    install -Dm644 README.md         "${pkgdir}/usr/share/doc/${pkgname}/README.md"
-    install -Dm644 SECURITY.md       "${pkgdir}/usr/share/doc/${pkgname}/SECURITY.md"
-    install -Dm644 CHANGELOG.md      "${pkgdir}/usr/share/doc/${pkgname}/CHANGELOG.md"
-    install -Dm644 AUDIT.md          "${pkgdir}/usr/share/doc/${pkgname}/AUDIT.md"
-    install -Dm644 LICENSE           "${pkgdir}/usr/share/licenses/${pkgname}/LICENSE"
-
-    # Vendored libzuptsdk shipped alongside the binary because the binary
-    # is linked with -Wl,-rpath,$ORIGIN/vendor/zuptsdk. For system install
-    # we move it to /usr/lib/zupt/ and the binary's rpath remains relative.
-    install -d "${pkgdir}/usr/lib/${pkgname}"
-    install -Dm755 vendor/zuptsdk/libzuptsdk.so.2.0.0 \
-        "${pkgdir}/usr/lib/${pkgname}/libzuptsdk.so.2.0.0"
-    ln -sf libzuptsdk.so.2.0.0 "${pkgdir}/usr/lib/${pkgname}/libzuptsdk.so.2"
-    ln -sf libzuptsdk.so.2.0.0 "${pkgdir}/usr/lib/${pkgname}/libzuptsdk.so"
+    install -Dm644 README.md    "${pkgdir}/usr/share/doc/${pkgname}/README.md"
+    install -Dm644 SECURITY.md  "${pkgdir}/usr/share/doc/${pkgname}/SECURITY.md"
+    install -Dm644 CHANGELOG.md "${pkgdir}/usr/share/doc/${pkgname}/CHANGELOG.md"
+    install -Dm644 LICENSE      "${pkgdir}/usr/share/licenses/${pkgname}/LICENSE"
 }