Store the depth channel in an analysis result and serve it to the 2D depth view

A replay could draw arrows but not depth, and the recording view said there was
nothing to draw even when a result existed. Depth is now quantised per frame
(14 B empty, 486 B at the worst frame seen), read from the cache by the same
draw path live uses, and the raw-recording note appears only when no result
exists. Format version 2; see apps/studio/docs/replay-analysis.md.

apps/studio/config/locales/en_US.json

@@ -190,7 +190,7 @@
     "view_mode_tip": "Image display mode while running",
     "replay_pipeline": "Recorded video (raw camera image)",
     "replay_pipeline_tip": "Replay shows the recorded raw camera image with no live arrow overlay; to check the algorithm, use View → Recompute forces from the video",
-    "replay_raw_note": "A recording stores only the raw camera image: there is no flow or depth to draw. Use “Recompute from the video” for the algorithm's output",
+    "replay_raw_note": "A recording stores only the raw camera image: there is no flow or depth to draw, because this recording has no analysis result yet. Opening a recording runs the pass automatically, or press “Recompute from the video”; once a result exists this pane can draw arrows and the depth map",
     "frame_missing_note": "This frame carries no {fields}: there is nothing for this view to draw",
     "field_flow": "flow",
     "field_depth": "depth",
@@ -201,6 +201,7 @@
     "arrow_empty_tip": "The deformation arrow image appears here while running or previewing",
     "depth_unavailable": "No depth data for this frame\n(not a depth of zero, and no silent fallback to the processed image)",
     "depth_scale": "Depth scale {low} – {high}",
+    "depth_empty": "This frame's depth is all zeros (0 of {pixels} px non-zero): the ramp's low colour is a real zero response, not missing data",
     "arrow_scale": "Arrows: displacement ×{factor}",
     "arrow_scale_tip": "Display magnification of the relative displacement: the arrows are drawn from the algorithm output of the captured image, with the measured displacement multiplied by this factor and capped at 0.8 of the grid spacing (a capped arrow no longer shows its true factor).",
     "arrow_pipeline": "Captured image → algorithm output",

apps/studio/config/locales/zh_CN.json

@@ -190,7 +190,7 @@
     "view_mode_tip": "运行时的图像显示模式",
     "replay_pipeline": "录制视频（原始相机图像）",
     "replay_pipeline_tip": "回放显示的是录制下来的原始相机图像，不含实时箭头叠加；要复核算法请用「视图 → 由视频重算力值」",
-    "replay_raw_note": "录像只保存原始相机图像：这里没有光流/深度可画。要看算法处理结果，请用「由视频重算」",
+    "replay_raw_note": "录像只保存原始相机图像：这里没有光流/深度可画，因为这个录像还没有分析结果。打开录像会自动跑一遍分析，也可以点「由视频重算」手动生成；有结果后本面板就能画箭头和深度图",
     "frame_missing_note": "本帧没有{fields}：这个视图这一帧没有数据可画",
     "field_flow": "光流",
     "field_depth": "深度",
@@ -201,6 +201,7 @@
     "arrow_empty_tip": "运行或预览后在此显示形变箭头图",
     "depth_unavailable": "本帧没有深度数据\n（不是深度为零，也未回退显示普通形变图）",
     "depth_scale": "深度色标 {low} – {high}",
+    "depth_empty": "本帧深度全为 0（{pixels} px 中 0 个非零）：色标低端色是一帧真实的零响应，不是缺数据",
     "arrow_scale": "箭头按位移放大 ×{factor}",
     "arrow_scale_tip": "相对位移的显示放大倍率：箭头由原始采集图像经算法输出，长度按测量位移放大后绘制，上限为网格间距的 0.8 倍；触顶的箭头不再呈现真实倍率。",
     "arrow_pipeline": "原始图像 → 算法输出",