Add verified multipart Linux and Windows GitHub releases

docs/github-releases.md

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+# Downloadable releases
+
+The GitHub release provides playable Linux x86_64 and Windows x86_64 packages.
+Cargo, Python, the old engine and a Git checkout are unnecessary for play.
+
+The approved HD artwork makes the shared data larger than GitHub's
+[2 GiB limit per release asset](https://docs.github.com/en/repositories/releasing-projects-on-github/about-releases).
+Each platform ZIP therefore contains the executable, platform libraries, all
+45 mods with SD/HD artwork and audio, and the source/docs. Shared data ZIPs
+contain the complete unchanged original catalog, approved HD pack, briefings
+and the runtime manifest's other data files. Extracting them together produces
+one self-contained `RustRaptor` folder. A single ZIP is only part of the download.
+
+## Install
+
+Download `Install-Windows.ps1` or `Install-Linux.sh` from the release. Review it,
+then run it in a directory without an existing `RustRaptor` folder. It downloads
+your platform ZIP and every shared data ZIP, checks each archive and every extracted payload against the versioned
+`release-manifest.json` (and publishes `SHA256SUMS` for manual verification),
+and extracts them into the same destination. Downloads are processed one at a
+time. Linux needs Bash and Python 3.8 or later for this optional installer; Windows uses
+built-in Windows PowerShell 5.1 and .NET. The Windows helper uses explicit extended
+paths to retain long accepted proof filenames without an admin policy change.
+A failed install preserves its partial folder for inspection; move or remove that
+folder before retrying. All archives reject unexpected paths, links and file collisions.
+
+```powershell
+powershell -NoProfile -ExecutionPolicy Bypass -File .\Install-Windows.ps1
+```
+
+```sh
+bash ./Install-Linux.sh
+```
+
+For manual installation:
+
+1. Download **one** platform ZIP: `RustRaptor-windows-x86_64.zip` or
+   `RustRaptor-linux-x86_64.zip`.
+2. Download **every** `RustRaptor-data-NN-of-TT.zip` and `SHA256SUMS` from
+   the **same release**. Do not mix snapshots.
+3. Verify the downloaded hashes. On Windows use `Get-FileHash -Algorithm SHA256`;
+   on Linux use `sha256sum`. Compare them with `SHA256SUMS`.
+4. Extract every downloaded ZIP into the **same parent directory**. Every ZIP
+   starts with `RustRaptor/`; do not make a different subfolder for each ZIP.
+5. Start `RustRaptor/run.cmd` on Windows or `RustRaptor/run.sh` on Linux.
+
+Keep enough storage for the installed folder plus one data ZIP during install.
+The release notes state the exact installed/download sizes. Your pilots and
+settings stay in the separate `RaptorReplica` user profile directories.
+
+## Maintainer export
+
+Export only a clean, fully committed final tested commit with current Linux and Windows manifests.
+The exporter does not build, refresh the runtime, change manifests or upload.
+
+```sh
+python3 tools/export_release.py plan --package . \
+  --expected-commit FULL_TESTED_COMMIT --output /tmp/release-plan.json
+python3 tools/export_release.py archive --plan /tmp/release-plan.json \
+  --asset RustRaptor-data-01-of-07.zip \
+  --output /tmp/RustRaptor-data-01-of-07.zip \
+  --receipt /path/to/receipts/RustRaptor-data-01-of-07.zip.json
+```
+
+Use the actual volume count in the plan. Each asset is under 1.5 GB before ZIP
+overhead, is checked against every planned source SHA-256 while writing, and
+passes whole-archive CRC validation before a receipt is produced. The exporter
+retains Linux execute permissions. The exporter inventories selected source files without following symlinks and
+rejects non-regular members. It preserves every physical runtime-data file,
+including directories named `derived`; proof/lineage files already present in
+the runtime manifest remain included.
+
+Create a draft release at the exact tested tag. Write, verify and upload one
+archive at a time, record its remote size/digest, then remove only that disposable
+export copy before producing the next. Keep receipts. After all assets exist:
+
+```sh
+python3 tools/export_release.py checksums --plan /tmp/release-plan.json \
+  --receipts /path/to/receipts --output /tmp/SHA256SUMS \
+  --manifest-output /tmp/release-manifest.json --tag v0.1.0-preview.20261020
+```
+
+Upload the versioned release manifest, checksum list and installers, check complete remote membership, and
+publish the draft only after all checks pass. Native Windows CI and local
+representative rendering/audio evidence retain their actual commit and scope;
+archive integrity checks do not imply a fresh full playthrough.