Merge PR #1471 (rebased)

# Conflicts:
#	docs/parity-checklist.md

docs/camera-preview-colour.md

@@ -221,6 +221,18 @@ as the fitted table does, and the chroma curve has no DNG tag, so it is left out
 HDR merge of three copies of the photo against the photo alone (200 px, CIE76): mean ΔE 1.07 and 0.47, 95th
 percentile 2.65 and 1.15 (26 and 23 before, with no colour tags; 1.47 and 0.66 with the table left out too).
 
+A raw whose white balance is only in its vendor multipliers (CR2, NEF, ARW…) has no `AsShotNeutral` of its own, so a
+frame carries the multipliers (`Frame::wb_multipliers`) next to its colour tags. A panorama, and an HDR merge from its
+inputs, takes its white balance from the frames that are in it: the median R/G and the median B/G of their multipliers
+(the mean of the middle two for an even count; frames without usable multipliers, or outside the panorama, do not
+vote), written as `AsShotNeutral`, the reciprocal. Any `AsShotWhiteXY` of the source is dropped with it: a reader takes
+it first, and the DNG spec has the two exclude each other. So the result is balanced for what the camera measured for
+most of its frames, not for whichever frame came first; an HDR panorama's merged brackets vote with their bracket's
+median. With no multipliers anywhere (DNG sources) the reference or first frame's tags are kept as before. For frames
+balanced alike this is the neutral `starting_colour_tags` already wrote, so the merged DNG renders as before; it matters
+when the camera balanced the frames differently, and for a caller that loads frames without a colour hook
+(`load_frame`), whose raw frames carried no white balance at all (issue #1144).
+
 ## Nikon crop and preview colour metadata
 
 Nikon maker-note `CropArea` (0x0045) supplies the default `[left, top, width, height]` crop. The decoder validates the rectangle against the active sensor area and falls back to that area for missing or invalid values. The CFA origin is unchanged; cropping follows demosaicing.

docs/parity-checklist.md

@@ -351,8 +351,8 @@ differences and missing bindings are in [ui-parity.md](ui-parity.md#shortcuts).
 
 | Id | Feature | Tier | Status | Evidence | Missing / notes |
 |---|---|---|---|---|---|
-| LR-MERGE-HDR | HDR merge | P2 | 🟡 | `cmd:merge.hdr`, `cmd:dialog.mergeHdr`, `crates/merge/src/frame.rs` (`Frame::lens`), `crates/merge/src/hdr.rs` | auto align, deghost None–High + overlay, auto settings, float DNG, Create Stack; the DNG keeps the reference frame's embedded lens corrections (tested by `hdr_merge_keeps_the_reference_frames_lens_corrections`); raws without colour matrices of their own (CR2, NEF, ARW…) keep the colour they open with, written as DNG tags (`starting_colour_tags`; the look's chroma curve has no tag; panoramas too), issue #965. Tested on real Sony A7R VI brackets (67 MP, 2026-10-14): frames agree with the merged radiance within ~1 % in all channels, exposure steps match EXIF within 0.03 EV. A clipped highlight of the reference that moved in other frames (a star at 200 mm) stays instead of becoming a black hole, and deghost (≤ 2048 px maps) catches a brighter frame's ghost in a dark sky (`a_clipped_star_of_the_reference_is_not_erased_by_frames_where_it_moved`, `deghost_removes_a_bright_frames_ghost_in_a_dark_sky`). 🟡 because: AI Denoise doesn't run on merged DNGs (Bayer only; Lightroom's does), JPEG brackets are treated as linear (no camera response curve), and every frame is held as 32-bit float (~0.86 GB per 67 MP frame, so 7 frames need ~7 GB); gap 29 |
-| LR-MERGE-PANO | Panorama | P2 | ✅ | `cmd:merge.panorama`, `cmd:dialog.mergePanorama` | spherical/cylindrical/perspective + auto, boundary warp, auto crop, fill edges (diffusion), DNG; no lens model / 360° wrap |
+| LR-MERGE-HDR | HDR merge | P2 | 🟡 | `cmd:merge.hdr`, `cmd:dialog.mergeHdr`, `crates/merge/src/frame.rs` (`Frame::lens`), `crates/merge/src/hdr.rs` | auto align, deghost None–High + overlay, auto settings, float DNG, Create Stack; the DNG keeps the reference frame's embedded lens corrections (tested by `hdr_merge_keeps_the_reference_frames_lens_corrections`); raws without colour matrices of their own (CR2, NEF, ARW…) keep the colour they open with, written as DNG tags (`starting_colour_tags`; the look's chroma curve has no tag; panoramas too), issue #965; the DNG's `AsShotNeutral` is the median of the inputs' vendor white-balance multipliers, issue #1144. Tested on real Sony A7R VI brackets (67 MP, 2026-10-14): frames agree with the merged radiance within ~1 % in all channels, exposure steps match EXIF within 0.03 EV. A clipped highlight of the reference that moved in other frames (a star at 200 mm) stays instead of becoming a black hole, and deghost (≤ 2048 px maps) catches a brighter frame's ghost in a dark sky (`a_clipped_star_of_the_reference_is_not_erased_by_frames_where_it_moved`, `deghost_removes_a_bright_frames_ghost_in_a_dark_sky`). 🟡 because: AI Denoise doesn't run on merged DNGs (Bayer only; Lightroom's does), JPEG brackets are treated as linear (no camera response curve), and every frame is held as 32-bit float (~0.86 GB per 67 MP frame, so 7 frames need ~7 GB); gap 29 |
+| LR-MERGE-PANO | Panorama | P2 | ✅ | `cmd:merge.panorama`, `cmd:dialog.mergePanorama` | spherical/cylindrical/perspective + auto, boundary warp, auto crop, fill edges (diffusion), DNG whose `AsShotNeutral` is the median of its frames' as-shot white balance (vendor multipliers for CR2, NEF, ARW…), issue #1144; no lens model / 360° wrap |
 | LR-MERGE-HDRPANO | HDR panorama | P2 | ✅ | `cmd:merge.hdrPanorama`, `cmd:dialog.mergeHdrPanorama` | brackets grouped by EXIF |
 | LR-MERGE-HEADLESS | Merge with last settings | P2 | ✅ | `cmd:merge.hdrLast`, `cmd:merge.panoramaLast`, `cmd:merge.hdrPanoramaLast`, `cmd:merge.hdrBatch`, `crates/catalog/src/stacks.rs` (`bracket_sets`) | no dialog; the options of the last merge of that kind (defaults the first time). HDR for Each Bracket Set merges a batch like Lightroom's merge of stacks: one HDR per stack among the photos, then per bracket (photos taken less than a second apart, after the shutter time, at exposures ≥ ½ EV apart; bursts at one exposure are skipped), one after the other in the activity stack (cancelling one stops the rest; a failed set doesn't); CLI `merge hdr-batch FILES…` |
 
@@ -797,6 +797,8 @@ Latin stays upright. Advanced Japanese composition remains open. Regression cove
 |---|---|---|
 | 2026-10-12 | minor | LR-EDIT-OPTICS-PROFILE: Sony ARW shading, CA and distortion tables decoded with settings and provenance (raw IFD, `SR2SubIFD` fallback); applied corrections unchanged (ILCE-7RM4A and ILCE-7RM6 distortion); status unchanged (🟡) |
 | 2026-10-14 | minor | LR-IMP-CAMERA-COVERAGE: Camera-coverage sweep (#1327): 30 models verified on 40 CC0 files (coverage.py 515 → 545 verified); sensor verification does not establish colour parity (#1277); status unchanged (🟡) |
+| 2026-10-13 | minor | LR-MERGE-PANO: a panorama's DNG takes its `AsShotNeutral` from the median of its frames' vendor white-balance multipliers (CR2, NEF, ARW…) instead of the first frame's tags, and frames now carry the multipliers (issue #1144); status unchanged (✅) |
+| 2026-10-13 | minor | LR-MERGE-HDR: an HDR merge's DNG takes its `AsShotNeutral` from the median of its inputs' vendor white-balance multipliers instead of the reference frame's tags (issue #1144); status unchanged (🟡) |
 | 2026-10-14 | minor | LR-IMP-CAMERA-COVERAGE: 17 uncompressed Olympus and Samsung Adobe models verified on one CC0 file each; status unchanged (🟡) |
 | 2026-10-13 | minor | LR-EDIT-SECTION-SOLO: Solo Mode for Edit sections (Window ▸ Edit Sections, section-header menu, ⌥-click); KEYC-PANELS notes it |
 | 2026-10-14 | minor | LR-MERGE-HDR ✅ → 🟡: tested on real 67 MP Sony brackets; moving clipped highlights (black-hole stars) and dark-sky ghosts fixed, merge memory cut ~25 %; AI Denoise on merged DNGs, JPEG response curves and per-frame memory remain (gap 29). LR-MERGE-HEADLESS, MENU-PHOTO-MERGE: HDR for Each Bracket Set (`merge.hdrBatch`) |