LR-HDR-EXPORT: HLG HDR AVIF export (hdrTransfer) and a tested SDR/HDR display decision

AVIF HDR export takes hdrTransfer = pq | hlg (export dialog: HDR curve;
MCP export schema lists it). HLG writes CICP transfer 18 and no clli box.
The window logs whether it shows HDR; today always SDR (eframe configures
an 8-bit surface), with the platform / surface format / headroom / opt-out
rules unit-tested. Also satisfies clippy 1.99's chunks_exact_to_as_chunks
in spots.rs.

Part of #868.

Sources: ITU-R BT.2100 (HLG OETF, inverse OOTF with system gamma 1.2),
ITU-R BT.2408 (203 cd/m2 reference white at 75 % HLG); own design for
the display decision.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

docs/gaps.md

@@ -1,6 +1,6 @@
 # Gaps: where LightCraft falls short of Lightroom
 
-> **Last reviewed:** 2026-10-11 · **Last updated:** 2026-10-11 · **Change:** minor (CR3 entry names the EOS R7 C-RAW fix and the refused CRX variants; CI and Windows / Linux entries note the 0.6.0 riscv64 build; camera colour: tone curve from black-and-white camera JPEGs; Compare and Reference get sharp zoom windows; gap 4 shrinks; gap 14: the HDR switch is read from crs XMP; gaps 2 and 10: EOS R5 Mark II CR3 verified) · **Target:** Adobe Lightroom Classic 15.5 / Lightroom 9.6
+> **Last reviewed:** 2026-10-11 · **Last updated:** 2026-10-12 · **Change:** minor (gap 14: HLG AVIF export done, HDR display decision tested); previously minor (CR3 entry names the EOS R7 C-RAW fix and the refused CRX variants; CI and Windows / Linux entries note the 0.6.0 riscv64 build; camera colour: tone curve from black-and-white camera JPEGs; Compare and Reference get sharp zoom windows; gap 4 shrinks; gap 14: the HDR switch is read from crs XMP; gaps 2 and 10: EOS R5 Mark II CR3 verified) · **Target:** Adobe Lightroom Classic 15.5 / Lightroom 9.6
 
 Every known shortfall, one entry each, ranked by user impact (how many Lightroom users hit it, and
 how hard it blocks them), then by effort. **Agents pick work from the top** (the first entry nobody is
@@ -28,7 +28,7 @@ Hours are Opus 5.5 agent wall-clock hours (see [target-app-parity.md](target-app
 | 11 | **Enhance: Raw Details, Super Resolution; AI denoise without shippable weights or X-Trans** | ENH rows 0%; denoise Bayer only, RawNIND weights GPL and opt-in | Fujifilm users get no AI denoise; nobody gets it out of the box | 30–60 + model decision | [raw-parity](raw-parity.md#demosaic-levels-crops-and-lens-metadata) |
 | 12 | **Content-aware / generative remove, detect distractions, reflections removal** | REM rows 75%; patch synthesis missing | cleanup work goes back to Photoshop | 25–45 (+ generative model) | [target-app-parity](target-app-parity.md#ai) |
 | 13 | **Lightroom catalog migration is one-way and approximate**: unsupported Adobe profiles / AI settings archived, history kept as data | lightroom-catalog-import.md | switching users lose some looks | 8–12 | [file-format-parity](file-format-parity.md) |
-| 14 | **HDR display** (EDR / Windows HDR); HLG; the headroom limit and SDR rendition from `crs` XMP (the HDR switch, `HDREditMode`, is read) | HDR rows 70%; LR-VIEW-HDR-DISPLAY ⬜ | HDR editing works blind on HDR monitors | 12–25 | [hardware-parity](hardware-parity.md) |
+| 14 | **HDR display** (EDR / Windows HDR); the headroom limit and SDR rendition from `crs` XMP (the HDR switch, `HDREditMode`, is read). HLG AVIF export done; the display's SDR/HDR decision is tested, blocked on eframe's 8-bit surface | HDR rows 70%; LR-VIEW-HDR-DISPLAY ⬜ | HDR editing works blind on HDR monitors | 12–25 | [hardware-parity](hardware-parity.md) |
 | 15 | **Print module**: custom packages, printer colour management (contact-sheet PDF only) | LRC-PRINT rows | Classic users who print | 25–40 | [target-app-parity](target-app-parity.md#features) |
 | 16 | **Map view, Book, Slideshow module, publish services** | LRC-MAP / BOOK / SS rows ⬜ | Classic users; publish services matter for Flickr / SmugMug workflows | 60–100 | [target-app-parity](target-app-parity.md#features) |
 | 17 | **Tethered capture** | ⬜ | studio photographers | 25–45 + cameras | [hardware-parity](hardware-parity.md) |
@@ -72,6 +72,7 @@ Beta-blocking gaps (B) total **~230–430 h**; with the stability and platform w
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-12 | minor | Gap 14: HLG AVIF export (`hdrTransfer`) and a tested SDR/HDR display decision |
 | 2026-10-11 | minor | Reviewed against main after 0.6.0: CR3 entry names the CRX variants `crx.rs` still refuses and the R7 / R6 Mark II C-RAW state (decoding, not verified, so the measured numbers don't move); CI and Windows / Linux entries note the riscv64 release build (#844); R7 fix added to Closed recently. Panel docking (UI.9, #869) closes no listed gap |
 | 2026-10-11 | minor | Camera colour entry: raws with a black-and-white camera JPEG take its tone curve (#577); gap not closed |
 | 2026-10-11 | minor | Gap 4: Compare and Reference views get zoom windows per pane (1:1 was a 2,560 px render magnified); overlays and soft proofing remain, 8–15 h → 4–8 h |