Export: Targa (.tga) sequence output, 24-bit RGB or 32-bit RGB + Alpha

After Effects lists Targa among its still-image output formats; EffectCraft
imported Targa (#745) but could not render to it.

- OutputFormat::TargaSequence ("Targa Sequence", `.tga`, numbered like the
  other sequences; `tga` / `targa` as a format name or output extension).
- Written by the `image` crate's Targa encoder (its `tga` feature, already
  enabled in effectcraft-media; no new crates, Cargo.lock unchanged), with
  run-length compression off: an 18-byte header, top-left origin, 24-bit BGR
  for RGB, 32-bit BGRA with 8 alpha bits in the image descriptor for
  RGB + Alpha (straight or premultiplied), 8-bit grey for Alpha.
- The render queue's size estimate counts the uncompressed bytes.
- CLI usage, the renderQueue command specs, README, architecture.md and
  file-format-parity.md name the new format.

Tests: each Targa frame holds exactly the pixels of the PNG sequence of the
same job, with the expected header, numbering and size; the frames read back
through the Targa importer as the same picture (straight, and premultiplied
when interpreted so); the image-sequence round trip, the format parser and
the renderQueue commands cover it too.

docs/architecture.md

@@ -37,7 +37,7 @@ cpal or muda. Everything in L0 to L4, the egui UI and the web app also build for
 | L3 | `render` | Evaluation and compositing: sources, masks, effects, transforms, 3D, motion blur, mattes, blending, layer cache, audio mixdown |
 | L3 | `media` | Footage decoding (FilmCraft's pure-Rust codecs), image sequences, Photoshop and SVG stills, frame cache |
 | L3 | `expr` | The expression engine (JavaScript via boa) with the After Effects object model |
-| L3 | `export` | Render queue encoding: H.264, HEVC and AV1 MP4, ProRes, WebM (VP9 + alpha or AV1, Opus), PNG/JPEG/TIFF/EXR sequences, GIF, WAV/AIFF |
+| L3 | `export` | Render queue encoding: H.264, HEVC and AV1 MP4, ProRes, WebM (VP9 + alpha or AV1, Opus), PNG/JPEG/TIFF/EXR/Targa sequences, GIF, WAV/AIFF |
 | L3 | `gpu` | The GPU compositor and GPU effects on wgpu compute shaders (Metal, Vulkan, Direct3D 12, WebGPU), checked against the CPU renderer |
 | L3 | `interchange` | Premiere Pro interop through timeline interchange (FCP7 XML, FCPXML, OTIO, EDL, AAF, OMF via FilmCraft's `filmcraft-interchange`): sequences ↔ compositions (§6a) |
 | L3 | `lottie` | Lottie JSON / dotLottie import and export (layers, precomps, eased and spatial keyframes, shapes, masks, mattes) with a warnings list for what Lottie cannot express |

docs/file-format-parity.md

@@ -48,7 +48,7 @@ trips and renders, checked by tests, not against After Effects), **partial** (na
 | GIF | R/W | yes | yes (animated) | good |
 | BMP | R | yes | — | good |
 | WebP | — | yes (still; animated WebP as footage with its frames, timing and alpha, #762) | — | beyond After Effects |
-| Targa `.tga` | R/W | yes (still and sequence; alpha interpreted on import) | none | good for import (#745); no Targa output |
+| Targa `.tga` | R/W | yes (still and sequence; alpha interpreted on import) | yes (sequence; uncompressed 24-bit RGB or 32-bit RGB + Alpha, straight or premultiplied) | good: import (#745); output reads back through it unchanged; the alpha is not labelled in the file (no TGA 2.0 extension area), so it is interpreted on import |
 | DPX / Cineon `.dpx` `.cin` | R/W | yes (still and sequence; 8/10/12/16-bit luma, RGB, RGBA, both byte orders; log code values shown as stored) | none | partial: import (#756); no Interpret Footage ▸ Cineon Settings (log to linear), no DPX output; common in film VFX |
 | Radiance `.hdr` | R/W | yes (still and sequence, 32-bit linear float like OpenEXR) | none | good for import (#745); no Radiance output |
 | SGI, PICT, ElectricImage, RLA/RPF images | R | none | none | Legacy; RPF camera data import exists (`keys.rpfCameraImport`) |
@@ -96,19 +96,19 @@ trips and renders, checked by tests, not against After Effects), **partial** (na
 | Mocha shapes | R (Mocha AE) | own documented JSON | — | Mocha's format is not public |
 | Vanishing Point `.vpe` | R | none | — | no public specification; the menu entry explains why |
 
-## Render queue outputs (`OutputFormat::ALL`, 13)
+## Render queue outputs (`OutputFormat::ALL`, 14)
 
 H.264 MP4, HEVC MP4, AV1 MP4, ProRes MOV, uncompressed 8-bit RGB / RGB + Alpha MOV (`raw `, + PCM;
-#372), WebM (VP9 or AV1 + Opus), PNG / JPEG / TIFF / OpenEXR sequences, animated GIF, WAV, AIFF.
+#372), WebM (VP9 or AV1 + Opus), PNG / JPEG / TIFF / OpenEXR / Targa sequences, animated GIF, WAV, AIFF.
 Missing against After Effects + Media Encoder: 16-bpc uncompressed, AVI and lossless-compressed
-single-file video (Animation / PNG codecs), DPX / Targa / Photoshop sequences, MXF, DNxHR, hardware
+single-file video (Animation / PNG codecs), DPX / Photoshop sequences, MXF, DNxHR, hardware
 encoders ([hardware-parity.md](hardware-parity.md)), and rendering safely over an existing file
 (#325).
 
 ## Estimate
 
 **≈ 130–230 h**: `.aep` / `.aepx` import 80–160 h (after the owner decision), wiring TGA / DPX /
-HDR / MXF / AVI / DNx import and DPX/TGA output 10–20 h, FBX animation and skinning, USD and Substance 20–40 h,
+HDR / MXF / AVI / DNx import and DPX output 10–20 h, FBX animation and skinning, USD and Substance 20–40 h,
 relinking 6–12 h, `.mogrt`-compatible templates 15–30 h (partly parallel with the rest).
 
 ## Revision history