Fix pruned FFmpeg release inputs

docs/platform-portability.md

@@ -221,8 +221,10 @@ VM op 0x236 (non-modal) / op 0x20f (modal) / op 0x24d (green-mask transition)
 
 Everything before and after the selected decoder is portable. The replacement decision is an in-process
 FFmpeg backend behind a project-owned C ABI, not raw FFmpeg structs in Godot/C# and not a subprocess. FFmpeg
-`n8.1.2-29-g703dcc25b9` is pinned by immutable release URL and SHA-256 in each target manifest under
-`native/age_movie_ffmpeg/`; changing either pin requires rerunning the full installed-movie gate. The shim
+`n8.1.2-44-g7c533d0f86` is pinned by dated release URL, exact byte size, and SHA-256 in each target manifest under
+`native/age_movie_ffmpeg/`. BtbN prunes older dated autobuild releases, so upstream availability is not permanent:
+the current paired pin restores hosted builds, while a durable project-owned mirror remains necessary to prevent
+future 404-driven repins. Changing either pin requires rerunning the full installed-movie gate. The shim
 dynamically links an LGPL build made without GPL or nonfree components and uses
 `libavformat`, `libavcodec`, `libavutil`, `libswscale`, and `libswresample`. Release artifacts must carry
 the matching FFmpeg source/configuration and notices required by FFmpeg's

docs/tools-reference.md

@@ -291,18 +291,22 @@ send either the `step-limit` console block or the generated JSON.
 
 ## Native FFmpeg movie shim (Windows and Linux x64)
 
-The target-specific dependency manifests pin immutable LGPL shared FFmpeg archives and SHA-256 hashes. Windows
-development can use PowerShell/MSVC. Linux-hosted builds use Bash with Python 3, curl, MinGW-w64/binutils for the
-Windows target, a native C compiler/binutils for Linux, and the ordinary archive/core utilities available.
+The target-specific dependency manifests pin dated LGPL shared FFmpeg archives by exact byte size and SHA-256.
+BtbN prunes older dated autobuild releases, so the bytes are immutable while retained but their upstream URLs
+are not permanent; a failed 404 requires a paired manifest repin and full native/movie validation, while a
+project-owned durable mirror remains the long-term fix. Bootstrap downloads remove partial files on HTTP failure
+before validating the complete archive. Windows development can use PowerShell/MSVC. Linux-hosted builds use Bash
+with Python 3, curl, MinGW-w64/binutils for the Windows target, a native C compiler/binutils for Linux, and the
+ordinary archive/core utilities available.
 
 | Tool | Purpose | Run | Reads → Writes |
 |---|---|---|---|
-| `native/age_movie_ffmpeg/bootstrap-win64.ps1` | Download, hash-check, extract, and version-check the pinned FFmpeg SDK. Returns the resolved SDK root. | `.\\native\\age_movie_ffmpeg\\bootstrap-win64.ps1 [-Destination <dir>]` | `dependency-win64.json`, network/archive cache → disposable `build/downloads/`, `build/ffmpeg-sdk/` |
+| `native/age_movie_ffmpeg/bootstrap-win64.ps1` | Download, size/hash-check, extract, and version-check the pinned FFmpeg SDK. Returns the resolved SDK root. | `.\\native\\age_movie_ffmpeg\\bootstrap-win64.ps1 [-Destination <dir>]` | `dependency-win64.json`, network/archive cache → disposable `build/downloads/`, `build/ffmpeg-sdk/` |
 | `native/age_movie_ffmpeg/build-win64.ps1` | Discover the MSVC x64 toolchain, build `age_movie_ffmpeg.dll`, and stage its exact shared-library/license dependencies. | `.\\native\\age_movie_ffmpeg\\build-win64.ps1 -SdkRoot <bootstrap-output> [-OutputDirectory <dir>]` | C ABI source + FFmpeg SDK → disposable `build/native/win-x64/` by default |
-| `native/age_movie_ffmpeg/bootstrap-win64.sh` | Download, SHA-256-check, and extract the exact pinned Windows FFmpeg SDK, including its MinGW import libraries. Prints the resolved SDK root. | `native/age_movie_ffmpeg/bootstrap-win64.sh [destination]` | `dependency-win64.json`, network/archive cache → disposable `build/downloads/`, `build/ffmpeg-sdk/` |
+| `native/age_movie_ffmpeg/bootstrap-win64.sh` | Download, size/SHA-256-check, and extract the exact pinned Windows FFmpeg SDK, including its MinGW import libraries. Prints the resolved SDK root. | `native/age_movie_ffmpeg/bootstrap-win64.sh [destination]` | `dependency-win64.json`, network/archive cache → disposable `build/downloads/`, `build/ffmpeg-sdk/` |
 | `native/age_movie_ffmpeg/build-win64.sh` | Cross-build the AMD64 PE shim with MinGW, stage exactly five FFmpeg DLLs and the license, and run the static native-bundle contract gate. `MINGW_CC` and `MINGW_OBJDUMP` may override the standard tool names. | `sdk_root="$(native/age_movie_ffmpeg/bootstrap-win64.sh)"` then `native/age_movie_ffmpeg/build-win64.sh "$sdk_root" [output-directory]` | C ABI source + Windows FFmpeg SDK → disposable `build/native/win-x64/` by default, including `verification.json` |
 | `tools/verify_windows_native.py` | Without executing Windows code, require the exact native bundle, AMD64 PE architecture, all seven ABI exports and five FFmpeg imports, and no Cygwin/MSYS compatibility runtime. Optionally writes the machine-readable verification report used by later packaging. | `python3 -X utf8 tools/verify_windows_native.py <bundle> [--objdump <MinGW-objdump>] [--report <json>]` | disposable Windows native bundle → stdout and optional JSON report |
-| `native/age_movie_ffmpeg/bootstrap-linux-x64.sh` | Download, SHA-256-check, extract, and version-check the pinned Linux x64 FFmpeg SDK. Prints the resolved SDK root. | `native/age_movie_ffmpeg/bootstrap-linux-x64.sh [destination]` | `dependency-linux-x64.json`, network/archive cache → disposable `build/downloads/`, `build/ffmpeg-sdk/` |
+| `native/age_movie_ffmpeg/bootstrap-linux-x64.sh` | Download, size/SHA-256-check, extract, and version-check the pinned Linux x64 FFmpeg SDK. Prints the resolved SDK root. | `native/age_movie_ffmpeg/bootstrap-linux-x64.sh [destination]` | `dependency-linux-x64.json`, network/archive cache → disposable `build/downloads/`, `build/ffmpeg-sdk/` |
 | `native/age_movie_ffmpeg/build-linux-x64.sh` | Build the ELF64 x86-64 shim; stage the five exact FFmpeg SONAME libraries and license; reject stale `.so` files, unresolved/nonlocal FFmpeg dependencies, a missing `$ORIGIN` runpath, or a glibc requirement newer than the pinned 2.28 baseline. | `sdk_root="$(native/age_movie_ffmpeg/bootstrap-linux-x64.sh)"` then `native/age_movie_ffmpeg/build-linux-x64.sh "$sdk_root" [output-directory]` | C ABI source + FFmpeg SDK → disposable `build/native/linux-x64/` by default |
 | `tools/movie-corpus-gate` | Discover every MPEG program stream stored under an `.AGF` catalog entry; decode every video frame and, when present, every audio block through the unpaced FFmpeg session; validate independent sequence dimensions, metadata, RGBA size, stereo finite PCM, monotonic video/audio timestamps, EOF, timeout, and teardown; then emit a per-asset JSON report. Audio fields include sample rate/channels, block and PCM-frame counts, first/last PTS, signal presence, and decode time. Exit 0 means the expected corpus count and every asset passed; exit 1 is a gate failure; exit 2 means the native shim is absent. | `dotnet run --project tools/movie-corpus-gate -- --output build/movie-corpus-ffmpeg.json --expected-count 213 --max-item-ms 30000` · optional `--native-dir <dir>` | `SYS4INI.BIN` + loose/ALF VFS assets + staged FFmpeg shim → stdout progress + disposable `build/movie-corpus-ffmpeg.json` |