feat(quality): score every face on sharpness and alignment before it is evidence

Every embedding now carries the quality of the input it came from. Both
axes fall out of the AR-005 warp for free: crop_sharpness() is the
normalised Laplacian variance over the aligned 112x112, so contrast and
size cannot leak into it, and the alignment residual is the part of the
landmark deformation a similarity transform cannot explain, so in-plane
roll reads as zero and foreshortening does not.

Carried, not consumed. Nothing discounts or thresholds on either number
yet -- that is AR-030 and VR-012, and the knee has to be located against
recorded data before a gate is chosen. What this change buys is that the
data exists to locate it with.

No face is admitted unscored: the -1 sentinel is preserved rather than
clamped, and a degenerate landmark fit is counted rather than silently
dropped.

Takes the VR-001 dump to schema_version 2. The bump is not for readers,
which check for the datasets by name and replay a v1 dump unchanged; it
is so a consumer can tell "never scored" from "scored zero", which is
not recoverable from the arrays afterwards.

TRACES: AR-028, AR-029, AR-030 | VR-001 | SR-002

scripts/optimizer/SCHEMA.md

@@ -1,4 +1,4 @@
-# Embedding-dump HDF5 schema (v1)
+# Embedding-dump HDF5 schema (v2)
 
 One file per analysed title. Captures the pipeline state at the `EmbeddedSceneFrame`
 channel — i.e. after decode → detect → align → embed, but **before** tracking and
@@ -18,7 +18,7 @@ variable-length HDF5 types and reads straight into numpy.
 ```
 /                                     (root)
   attrs:
-    schema_version : int   = 1
+    schema_version : int   = 2
     embed_dim      : int   = 512
 
     # ── what produced the vectors (GR-004) ──────────────────────────────────
@@ -60,6 +60,12 @@ variable-length HDF5 types and reads straight into numpy.
     landmarks      : float32 [N, 10]  5 (x,y) pairs, SCRFD/ArcFace order,
                                       same space as bbox
     confidence     : float32 [N]      detector confidence
+
+    # ── embedding input quality (AR-028), v2 onward ─────────────────────────
+    sharpness          : float32 [N]  normalised Laplacian variance on the
+                                      112x112 aligned crop (AR-029)
+    alignment_residual : float32 [N]  RMS landmark misfit in canonical px,
+                                      after the AR-005 similarity fit (AR-030)
 ```
 
 `F` = number of sampled frames, `N` = total faces (= sum of face_count).
@@ -87,8 +93,9 @@ exactly the fact the committed fixtures needed to state.)
 Reading is by name with a default or an existence check on **both** sides —
 `replay.py` (`f.attrs.get(...)`) and `read_dump_provenance()` in
 `src/nodes/embedding_dump_node.hpp` (`attrExists`). So the attributes are
-additive and `schema_version` stays 1: a pre-VR-010 dump still loads, and a
-post-VR-010 dump still reads on old code.
+additive and did not themselves move `schema_version` off 1: a pre-VR-010 dump
+still loads, and a post-VR-010 dump still reads on old code. (AR-028 later took
+it to 2 by adding *datasets* — see below.)
 
 A missing attribute means **unknown**, never a default value. Substituting
 `detector_conf = 0.5` for a dump that does not say so manufactures the provenance
@@ -97,6 +104,40 @@ provenance is unknown is worse than no fixture, because it will be trusted."*
 The committed `tests/fixtures/dumps/*.h5` predate VR-010 and carry none of these
 attributes; re-dump to bind them, as with GR-004.
 
+## Embedding input quality (AR-028) — and why this one bumps the version
+
+`sharpness` and `alignment_residual` are two of the three AR-028 quality axes,
+written beside the embedding they describe. **The third axis, size, is already
+here**: it is `bbox`, scaled by `bbox_upscale` to reach the original resolution
+AR-002 thresholds in. It is not duplicated into a third column, because that
+would put the same quantity in two coordinate spaces inside one file — the trap
+the `bbox_upscale` note below records — and the copy is the one that drifts.
+
+The vector is **carried, not consumed**. Nothing in the pipeline thresholds or
+discounts on it yet; VR-012 locates the knees from these columns, which is only
+possible if they were recorded at inference. A study cannot recover how sharp a
+face was from an embedding, any more than it can recover which model produced it.
+
+**This is the change that bumps `schema_version` to 2**, where VR-010's
+attributes did not. The rule is unchanged — a bump is for the *datasets* — and
+so is the reason behind it. Readers are fine either way: `replay.py` and
+`test_replay_fixtures.cpp` take these datasets by name with an existence check,
+so a v1 dump still replays and loses only what it never had. The version exists
+for a *consumer of the quality vector*, which otherwise cannot tell **"this
+film's faces were never scored"** from **"this film's faces scored zero"** —
+sharpness 0 is a real reading, meaning a featureless crop. That is the same
+distinction `scene_detect` exists to make, and it is equally unrecoverable from
+the arrays.
+
+A v1 dump reports the vector as **unknown, never as a default** — `load_frames`
+omits the keys rather than filling zeros, and the C++ side leaves the
+`DetectedFace` fields at their -1 "unscored" sentinel. Re-dump to acquire it;
+there is no migration, for the same reason GR-004 has none.
+
+> The committed `tests/fixtures/dumps/*.h5` are v1 and carry no quality vector.
+> Re-dumping needs a GPU host (`scripts/make_fixtures.sh`), so until that runs,
+> anything driven from the fixtures sees the sentinel.
+
 ## Model binding (GR-004)
 
 `embedder_model` / `embedder_sha256` record which embedder produced every vector
@@ -144,3 +185,7 @@ one never received. Two further reasons:
   original resolution (see above).
 - A frame with no faces has `face_count == 0` (still gets a row, so timestamps stay dense).
 - EOF sentinel frames are NOT written.
+- v2 onward: `sharpness` and `alignment_residual` are `[N]`, parallel to
+  `confidence`, so face *i*'s quality indexes with the same slice as its
+  embedding. Both are `>= 0` for any face the aligner admitted; a negative value
+  means unscored and must never be read as a quality.