#783: Object Matte fidelity plan; gaps and parity notes updated

Problem: Object Matte had no After Effects comparison, and none can be made
on this Linux machine (no After Effects). The gap notes still listed the
viewer tool, background job and disk cache as missing.

Fix: docs/fidelity/object-matte.md states plainly that nothing is measured
yet and pins down the comparison for when an After Effects 26.2+ reference
is available: four original or openly licensed clips (the synthetic moving
disk from the engine tests, the disk with a jump, two objects with a box
prompt, one CC0/CC BY real clip), the prompt and settings, where reference
mattes stay (gitignored), and the metrics: per-frame IoU against After
Effects (headline), IoU against ground truth, boundary distance, soft-edge
error, temporal stability, drift and time per frame, plus a proposed pass
bar left to the maintainers. Linked from docs/fidelity/README.md.
docs/gaps.md (#14) and docs/target-app-parity.md now list what landed and
leave the comparison as the one remaining item.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/fidelity/README.md

@@ -3,6 +3,9 @@
 The [AE 2026 replacement acceptance gates](ae-2026-acceptance.md) define the broader
 target across workflows, rendered output, work-project compatibility, performance and platforms.
 
+[Object Matte](object-matte.md) has a comparison plan (clips, prompt, per-frame IoU and the other
+metrics) but no measurement yet.
+
 The first G1 comparison measures eight original scalar Rotation cases against a live After Effects
 2026 session through AEsync 2.0.4: Easy Ease, overlapping influences, asymmetric ease, overshoot,
 descending values, equal endpoints, 100%/100% influence and 0.1%/100% influence. Each case has