crawler: --no-cover, --concurrency, drop cross-host sleep + batch-50 Step 1 done

Three crawler ergonomics for batch operations:

--no-cover  Skip cover image download. For scan-only modes (license/meta
            scrape) this drops ~1.3s/project and avoids slow-CDN hangs.

--concurrency N  ThreadPoolExecutor wrapping the per-project loop. Default
                 1 = serial (current behavior). Anonymous endpoints tolerate
                 5+ comfortably; output uses a print lock for readable
                 interleaved progress. fetch_cover plumbs through crawl_one.

Drop cross-host sleep #1: in crawl_one between detail HTML (oshwhub.com)
and cover image (image.lceda.cn). Different hosts — sleep was unnecessary.
Saves ~1s/project. Sleep #2 (post-cover, before next iteration) stays — it
gates the next oshwhub.com hit.

download_to gains max_seconds wall budget (default 60s, cover uses 15s).
Defends against pathologically slow CDN connections — observed 10 KB/s
on image.lceda.cn for one project, would have hung 6+ min on a 3.6 MB
cover otherwise. httpx default timeout resets per chunk, so streaming
downloads need an external wall-clock guard.

batch-50 Step 1 (license/meta scrape) shipped:
  50/50 candidates have metadata.json + license recorded
  License distribution: GPL 3.0 32, Public Domain 6, NC variants 8,
                        CERN-OHL 1, MIT 1, CC BY 3.0 1
  Forge-friendly (non-NC): 41/50 (82%)
  Declared attachments: 180 files / 2.36 GB (median 18 MB/proj, max 304 MB)
  Walltime: 3min 26s for 28 projects at concurrency=5 (server-side
            HTML render bound, not sleep-bound)

One orphan partial cover (a670e60a...) cleaned up — leftover from the
first aborted run before the timeout fix landed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

data/raw/oshwhub/ddcc963f6e234ee5b25bdf62d13c4a6b/metadata.json

@@ -0,0 +1,113 @@
+{
+  "source": "oshwhub",
+  "source_url": "https://oshwhub.com/bryan_he/usb_dc_ps",
+  "project_id": "ddcc963f6e234ee5b25bdf62d13c4a6b",
+  "title": "【星火计划】USB可编程电源/功率监测",
+  "description_short": "【星火计划】USB可编程电源/功耗监测，小程序控制，\n支持USB PD3.0，BC1.2协议，支持5V~20V输入，\n宽范围的输出电压，从2.7V ~ 20V可调，3A的带载能力",
+  "description_path": "description.md",
+  "author": {
+    "username": "bryan_he",
+    "display_name": "黑马小乌龟",
+    "user_id": "1eb895ea1970464ba4a8e4a1565b0830"
+  },
+  "license": "GPL 3.0",
+  "tags": [],
+  "created_at": "2024-01-10T09:31:52.000Z",
+  "updated_at": "2025-12-22T15:18:17.000Z",
+  "published_at": "2024-11-01T06:26:49.000Z",
+  "crawled_at": "2026-04-28T17:00:22.767489+00:00",
+  "metrics": {
+    "likes": 928,
+    "stars": 1578,
+    "forks": 0,
+    "views": 112602,
+    "watch": 0,
+    "comments": 389
+  },
+  "cover": {
+    "url": "https://image.lceda.cn/pullimage/Lrf0ZtIUAbrwgDC24lEzoJTsYs5s5klsd8n0YPay.jpeg",
+    "path": "cover.jpeg"
+  },
+  "files": [
+    {
+      "name": "LCD-手册.pdf",
+      "url": "https://image.lceda.cn/attachments/2024/3/EWpEH4sOZTa52mv3e12JQri5MbCkrvYrXsy5TPBl.pdf",
+      "original_id": "cc1c21030b24497caf390824b488828c",
+      "ext": "pdf",
+      "mime": "application/pdf",
+      "size": 999422,
+      "md5": "f07122c786a9c6e453d6c100d8af4182"
+    },
+    {
+      "name": "MCU-固件下载.mp4",
+      "url": "https://image.lceda.cn/attachments/2024/4/BjcxER2jGebgyCyJrMdYaeDjgbMhapSIE1nCwCtf.mp4",
+      "original_id": "176ce2712acd4727b932ad42aa7dae87",
+      "ext": "mp4",
+      "mime": "video/mp4",
+      "size": 26909130,
+      "md5": "cd78e9107a0642eb8efd0399718e4a75"
+    },
+    {
+      "name": "蓝牙固件下载.mp4",
+      "url": "https://image.lceda.cn/attachments/2024/4/x81B348S64e6ZdgyWK3hdjLlCBJKYHU1zmRkLrkV.mp4",
+      "original_id": "906f76602007450f8eb1541a10a9e9ca",
+      "ext": "mp4",
+      "mime": "video/mp4",
+      "size": 38613696,
+      "md5": "b745047e5b57b188966132b35f089760"
+    },
+    {
+      "name": "设备操作演示.mp4",
+      "url": "https://image.lceda.cn/attachments/2024/4/EdEXZFZHiEAKi4rzXCrRWEUHqZT70CePpxDNW2wx.mp4",
+      "original_id": "cc47b83886d7433f9cf106ca2bb11235",
+      "ext": "mp4",
+      "mime": "video/mp4",
+      "size": 49210029,
+      "md5": "2b6e07facb96b44873272b1647fd9ec4"
+    },
+    {
+      "name": "uart2ble_tools.7z",
+      "url": "https://image.lceda.cn/attachments/2024/4/uhB3dYov7WpxXRnIWeHrPC8nmkGRozLLnfMEBrxe.7z",
+      "original_id": "a0eeadb7dd29424482257676e0c27248",
+      "ext": "7z",
+      "mime": "application/octet-stream",
+      "size": 13361594,
+      "md5": "b3ce346bb3befc4b47486f2abf9ca0d7"
+    },
+    {
+      "name": "亚克力-up_shell.stp",
+      "url": "https://image.lceda.cn/oshwhub/project/attachments/cf6eb929e472480a89be3661e7780a3b.stp",
+      "original_id": "84b90cb41b514b40b106fc730abf1648",
+      "ext": "stp",
+      "mime": "application/octet-stream",
+      "size": 60509,
+      "md5": "ef9506c7aa0dbcfca6afc0c13ee7dd75"
+    },
+    {
+      "name": "亚克力-dw_shell.stp",
+      "url": "https://image.lceda.cn/oshwhub/project/attachments/c44dda8d22a14c2894290a240818c4fa.stp",
+      "original_id": "d9561ee14ea7445eb73a31cec0c82f2b",
+      "ext": "stp",
+      "mime": "application/octet-stream",
+      "size": 28449,
+      "md5": "ef5cd6624e193ba7a6062f159665b2c1"
+    },
+    {
+      "name": "usb-power-supply-v2-sw-v2.3.hex",
+      "url": "https://image.lceda.cn/oshwhub/project/attachments/e87e7a232cdc48a39606636ab90dc5d8.hex",
+      "original_id": "43d0d5423a6343c2a1f921217542b964",
+      "ext": "hex",
+      "mime": "application/octet-stream",
+      "size": 213791,
+      "md5": "782a8233d968d7da31601d546e1decde"
+    }
+  ],
+  "raw_fields": {
+    "path": "bryan_he/usb_dc_ps",
+    "grade": 4,
+    "origin": "pro",
+    "public": true,
+    "publish": true,
+    "skipped_files": []
+  }
+}