feat(playground): image & video generation tabs + real chat metrics

The infosave collection now ships media models (Lumina-Image-2.0, MiniMax-H3
Turbo) that cortiq runs via `imagine`/`animate` CLI, not `cortiq serve`. The
gateway grows a media API: local .cmf files are classified by `cortiq info`
(chat/image/video, cached), generations run as tracked jobs with step progress
parsed from stdout, one at a time, cancellable, outputs under <data>/media.

The playground becomes three tabs. Image: width/height/steps/CFG/seed, live
progress, result rendered from P6 PPM to a canvas in the browser (PNG export
via toBlob). Video: frames/steps/quality/seed plus optional first/last
keyframes (rasterized to PPM client-side); the MJPEG+PCM AVI is decoded in JS
and played on a canvas synced to the wav — no ffmpeg on either side (mp4 remux
happens opportunistically when ffmpeg exists). A metrics card shows resolution,
steps, seed, total time, time per step/frame and file size.

Chat metrics: the local cortiq server sends no usage chunk in streams, so
token counts showed 0/0. tap_stream now injects one OpenAI-shaped usage event
ahead of [DONE] with the gateway's ~4-chars/token estimate, flagged
`cortiq_estimated`; the UI renders it as "≈ N / M" and adds tok/s and
time-to-first-token. Registration skips media packs (a `cortiq serve` entry
for a diffusion model would only fail) in both Register and the wizard's
Finish.

36 new UI strings translated across all 7 languages.

web/js/i18n/zh.js

@@ -468,4 +468,42 @@ export default {
   "onboarding.deleteFile": "从磁盘删除该 .cmf 文件",
   "onboarding.confirmDelete": "删除 “{id}”？该 .cmf 文件将从磁盘移除。",
   "onboarding.unregistered": "同时已取消注册：{ids}",
+
+  // playground: media generation + streaming metrics
+  "pg.tab.chat": "对话",
+  "pg.tab.image": "图像",
+  "pg.tab.video": "视频",
+  "pg.generate": "生成",
+  "pg.generating": "生成中……",
+  "pg.genFailed": "生成失败 — 请查看日志。",
+  "pg.result": "结果",
+  "pg.genMetrics": "生成指标",
+  "pg.imagePromptPlaceholder": "夕阳下雪地里的红狐狸，照片级真实感，毛发细节丰富",
+  "pg.videoPromptPlaceholder": "戴厨师帽的柯基翻煎饼，滋滋声和欢快的犬吠",
+  "pg.imageEmpty": "生成的图像将显示在这里。",
+  "pg.videoEmpty": "生成的短片（含音频）将显示在这里。",
+  "pg.width": "宽度",
+  "pg.height": "高度",
+  "pg.steps": "步数",
+  "pg.seed": "Seed",
+  "pg.randomSeed": "随机 seed",
+  "pg.cfgHint": "引导强度；≤ 1 关闭 CFG，工作量减半。",
+  "pg.frames": "帧数",
+  "pg.framesHint": "24 fps；按模型网格取整。",
+  "pg.quality": "JPEG 质量",
+  "pg.videoSizeHint": "32 的倍数；训练短边为 768。",
+  "pg.videoStepsHint": "Turbo LoRA 按 4 步训练。",
+  "pg.firstFrame": "首帧（可选）",
+  "pg.lastFrame": "末帧（可选）",
+  "pg.keyframeHint": "使运行变为关键帧生视频。",
+  "pg.resolution": "分辨率",
+  "pg.genTime": "生成耗时",
+  "pg.timePerStep": "每步",
+  "pg.timePerFrame": "每帧",
+  "pg.fileSize": "文件大小",
+  "pg.duration": "时长",
+  "pg.play": "播放",
+  "pg.noMediaModels": "还没有本地{kind}模型。请在“导入模型”中下载一个（例如 infosave 合集）：",
+  "pg.tokSpeed": "速度",
+  "pg.ttft": "首个 token",
 };