feat(imaging): add pure-Rust JPEG 2000 backend (#109)

docs/dependency-policy.md

@@ -49,6 +49,7 @@ All native boundaries have Linux, Windows, and macOS strategies:
 |---|---|---|---|
 | libopus 1.3+ | `pkg-config` package `opus` | vcpkg `opus` for MSVC; `pkg-config` for GNU | WebRTC voice crate |
 | OpenJPEG 2.5.4+ | `pkg-config` package `libopenjp2` | vcpkg `openjpeg` for MSVC; `pkg-config` for GNU | opt-in `jpeg2000` |
+| j2k 0.8.1 | pure Rust, no platform prerequisite | same pure-Rust graph | opt-in `rust-j2k` |
 | Skia 0.99.0 | target-specific official binary cache or source build | same target-specific strategy | opt-in `skia` |
 | Vorbis 0.5.6 stack | `vorbis_rs` builds its reviewed C codec stack | same crate strategy | opt-in `vorbis` |
 | Physical audio | ALSA development files on Linux; CoreAudio is system-provided on macOS | WASAPI is system-provided | opt-in `real-audio` |

docs/imaging-meshing.md

@@ -17,12 +17,16 @@ and [`MeshFoundry` guide](../crates/libremetaverse-rendering-mesh-foundry/README
 | --- | --- | --- | --- |
 | Managed images and TGA | enabled | n/a | none |
 | JPEG 2000 | disabled | `libremetaverse-imaging/jpeg2000` | OpenJPEG 2.5.x |
+| JPEG 2000 (pure Rust) | disabled | `libremetaverse-imaging/rust-j2k` | none (`j2k` 0.8.1) |
 | BMP/GIF/ICO/JPEG/PNG/WBMP/WebP | disabled | `libremetaverse-imaging-skia/skia` | Skia |
 | Prim and sculpt meshing, OBJ ingestion | enabled | n/a | none |
 
 OpenJPEG is a non-default workspace member so release tooling can package the
 adapter explicitly, and imaging reaches it only through the optional
-dependency. Skia is likewise an optional, target-specific dependency. The
+dependency. The independent `rust-j2k` feature reaches only the audited
+pure-Rust `j2k` graph; enabling both features keeps both explicit codec types
+available for interoperability testing. Skia is likewise an optional,
+target-specific dependency. The
 consolidated required Gitea gate exercises both optional features on
 `ubuntu-latest` while its minimal-feature check proves that no native codec is
 needed for the owned Rust and translated compatibility tests.

docs/release-candidate.md

@@ -23,6 +23,7 @@ Optional boundaries are explicit:
 | Feature | Capability | Native/build prerequisite |
 | --- | --- | --- |
 | `jpeg2000` | J2K/JP2 through the safe OpenJPEG adapter | OpenJPEG 2.5.4 or newer |
+| `rust-j2k` | J2K/JP2 through `RustJ2kCodec` | none; exact pure-Rust `j2k` 0.8.1 |
 | `skia` | PNG/JPEG/WebP and other Skia formats | Skia 0.99 target cache or documented source tools |
 | `vorbis` | PCM to Ogg Vorbis | the locked `vorbis_rs` native build stack |
 | default WebRTC | native ICE/DTLS/SRTP/RTP/SCTP and Opus | system libopus 1.3 or newer |

docs/rust-api-guide.md

@@ -15,10 +15,10 @@ they use those APIs directly.
 
 | Crate | Choose it for | Features or system boundary |
 | --- | --- | --- |
-| `libremetaverse` | Grid client, login, network, agents, inventory, assets, appearance, world, and social APIs | Default pure-Rust BC6H/BC7; optional `jpeg2000` and `vorbis` |
+| `libremetaverse` | Grid client, login, network, agents, inventory, assets, appearance, world, and social APIs | Default pure-Rust BC6H/BC7; optional `jpeg2000`, `rust-j2k`, and `vorbis` |
 | `libremetaverse-types` | UUIDs, vectors, matrices, colors, cancellation, compatibility collections, and boundary types | Pure Rust |
 | `libremetaverse-structured-data` | LLSD/OSD XML, JSON, binary, and notation | Pure Rust |
-| `libremetaverse-imaging` | Managed images, TGA/DDS, codec traits | Optional `jpeg2000` |
+| `libremetaverse-imaging` | Managed images, TGA/DDS, codec traits | Optional `jpeg2000` or pure-Rust `rust-j2k` |
 | `libremetaverse-imaging-skia` | Common raster formats through Skia | Optional `skia`; native Skia build/cache |
 | `libremetaverse-prim-mesher` | Legacy prim and sculpt geometry | Pure Rust |
 | `libremetaverse-rendering-simple` | Deterministic reference geometry | Pure Rust |
@@ -190,6 +190,7 @@ The default client build needs no image-codec system library. Optional native
 features require:
 
 - `OpenJPEG` 2.5.4 or newer for `jpeg2000`;
+- no native prerequisite for the pure-Rust `rust-j2k` feature;
 - the rust-skia prerequisites/cache for `skia`;
 - system libopus for WebRTC voice and the `libremetaverse-opus` adapter;
 - ALSA development headers on Linux, `CoreAudio` on macOS, or WASAPI on Windows