v4.0.0: codec 2.60.4 security release, --pq-box sealed-box mode, F-16 fix

Major release. Highlights:

- Codec: vendored VaptVupt codec moves to canonical 2.60.4 security
  release. Fixes a high-severity OOB heap write in the AVX2 decode fast
  path (reachable on a valid stream sized to exactly content_size, both
  tail variants). Brings CBMC-formally-verified BCJ filters with
  automatic ELF/PE/Mach-O detection. Compressed output stays
  byte-identical (ratio gate Δ 0.00%); wire format unchanged at v1.6.
- New --pq-box sealed-box recipient mode (vendored libpqvaptvupt 0.6.0):
  ML-KEM-768 + X25519 combined via HKDF-SHA256 with domain separation,
  AES-256-CTR + HMAC-SHA256 EtM. Legacy --pq and --pq-sdk stay readable.
- F-16: discloses and fixes a pre-existing data-loss defect in the
  <= 3.8.0 in-tree BCJ encoder. Full back-compat matrix decodes
  byte-exact under 4.0.0; every readable pre-4.0 archive remains readable.

Repository hygiene:
- Sync full 4.0.0 source tree (codec, crypto, SDK, GUI, packaging, tests).
- Remove internal scratch files (PROMPT.md, FORMAL_AUDIT_PROMPT.md)
  and superseded version-specific docs (INTEGRATION_PROTOCOL_2.60.4.md,
  docs/FINDINGS-2.x.md) and a stray test binary.
- Refresh README download/install section to real 4.0.0 release assets;
  bump version badge to 4.0.0.
- Add .gitignore for build outputs (keeps vendored prebuilt libraries).

packaging/opensuse/README.md

@@ -0,0 +1,112 @@
+# openSUSE Build Service update for `home:cabelo:innovators/zupt`
+
+This directory contains the three files you need to update your OBS
+package from `1.5.5` to `2.4.8`:
+
+| File          | Status vs. your current files                                       |
+|---------------|---------------------------------------------------------------------|
+| `_service`    | Updated `revision` to `v2.4.8`. Format unchanged (still `tar_scm`). |
+| `zupt.spec`   | Version → `2.4.8`. License corrected `MIT` → `AGPL-3.0-or-later`. `%check` now calls `make check` (new distro-safe target). |
+| `zupt.changes`| 13 new entries prepended (2.0.0 → 2.4.8). Your existing 1.0.0–1.5.4 history is preserved verbatim. |
+
+## What changed in the spec
+
+1. **License correction** — your spec says `License: MIT`, but the
+   upstream license is **AGPL-3.0-or-later** (dual-licensed
+   AGPL-3.0-or-later + commercial). This was a bug that should
+   probably trigger a rebuild even without the version bump.
+
+2. **`%check` target** — your spec calls `test-all` on non-s390x
+   architectures. In v2.4.x, `test-all` includes threading tests
+   that are flaky on emulated build hosts (3 false positives on
+   x86_64 GitHub-Actions-style sandboxes). The new `make check`
+   target added in 2.4.8 runs a curated subset:
+
+   * F-06 HMAC tamper detection (2000 trials)
+   * F-08 archive-integrity-trailer
+   * F-09 byte-level integrity preface AAD
+   * F-10 KDF default
+   * F-11 auth-fail message
+   * F-12 encrypted comments
+   * NIST/RFC vectors (SHA-256, SHA-3, ML-KEM-768, AES-256-CTR,
+     HMAC, X25519, PBKDF2, Argon2id)
+   * Path-traversal, argument-order, block-swap regressions
+   * Quick smoke test
+
+   Total ~91 assertions, runs in <2 minutes, no flakes on emulated
+   hosts. The s390x branch still falls back to just `test-vectors`.
+
+3. **Upstream URL in `URL:` field** updated to
+   `https://git.securityops.co/cristiancmoises/zupt` (the canonical
+   project URL). The `_service` file still pulls from GitHub
+   (`https://github.com/cristiancmoises/zupt`) since that's where
+   your `tar_scm` is already configured and what works in OBS today.
+
+4. **`BuildRequires: make`** added — newer openSUSE chroots don't
+   always pull `make` in transitively. Harmless on older targets.
+
+5. **Docs** — `%doc README.md SECURITY.md CHANGELOG.md` now ships
+   the security boundary docs as well as the README. THREAT_MODEL.md
+   exists upstream but isn't listed here to keep the package small;
+   add `%doc THREAT_MODEL.md` if you want it included.
+
+## How to apply
+
+```sh
+# 1. Check out the package
+osc checkout home:cabelo:innovators zupt
+cd home:cabelo:innovators/zupt
+
+# 2. Drop the new files in (assuming this README is at
+#    /path/to/zupt-source/packaging/opensuse/README.md)
+cp /path/to/zupt-source/packaging/opensuse/_service     .
+cp /path/to/zupt-source/packaging/opensuse/zupt.spec    .
+cp /path/to/zupt-source/packaging/opensuse/zupt.changes .
+
+# 3. Trigger the service locally to fetch v2.4.8 from GitHub
+osc service runall
+
+# This produces zupt-2.4.8.tar.gz in the current directory and
+# updates zupt.changes with a service-generated entry if you have
+# changesgenerate enabled (you don't, so this is a no-op for
+# changes; tar_scm just downloads).
+
+# 4. (Optional) Local build to verify before committing
+osc build openSUSE_Tumbleweed x86_64
+
+# Expected: build succeeds, %check runs `make check`, all 10 suites
+# (~91 assertions) pass, package is produced.
+
+# 5. Commit upstream
+osc status   # confirm zupt-2.4.8.tar.gz is staged alongside the
+             # three text files
+osc commit -m "Update to 2.4.8: distro-safe make check target; license fix MIT -> AGPL"
+```
+
+## Notes for future updates
+
+* The `_service` `revision` is pinned to `v2.4.8`. To track a new
+  release, just edit that one line and re-run `osc service runall`.
+* The spec's `Version:` field is hard-coded — when you bump
+  `_service` `revision`, also bump `Version:` to match. The
+  `set_version` service in `_service` will auto-sync at OBS-build
+  time if you want; it's mode="manual" today, which is safer.
+* `BuildRequires` is intentionally minimal (just `gcc gzip make`).
+  Zupt has no external library dependencies — `libargon2`,
+  `libcrypto`, etc. used by other Linux packagers come from
+  *vendored* code that's compiled in. This is a deliberate
+  design choice; don't add system library BuildRequires.
+
+## Reporting issues
+
+* Upstream bugs: https://git.securityops.co/cristiancmoises/zupt
+* openSUSE packaging bugs: https://bugs.opensuse.org/
+* Cabelo's OBS project: https://build.opensuse.org/project/show/home:cabelo:innovators
+
+## Author of these update files
+
+Generated against upstream `zupt-2.4.8` source tree. Spec mirrors
+cabelo's existing 1.5.5 conventions (minimal `BuildRequires`,
+`%autosetup -p1`, `V=1` verbose build, `%ifarch s390x` branch in
+`%check`, no separate libzuptsdk subpackage) — only the necessary
+fields are changed.