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/48dd1b650d084739bef92ab8a651975a/_urls.json

@@ -0,0 +1,5 @@
+{
+  "detail_url": "https://oshwhub.com/wzw666/ip5389",
+  "cover_url": "https://image.lceda.cn/avatars/2021/10/GzDiNwDZSinZ1pfr44sY5cLLFIK0CGAKHSMmMJkK.png",
+  "attachments": []
+}

data/raw/oshwhub/48dd1b650d084739bef92ab8a651975a/description.md

@@ -0,0 +1,9 @@
+# IP5389[100瓦双向快充移动电源方案]
+
+100瓦双向快充移动电源方案
+
+---
+- Source: https://oshwhub.com/wzw666/ip5389
+- Author: 小煜哥哥 (wzw666)
+- License: CC-BY-NC-SA 3.0
+- Published: 2022-09-13T01:15:55.000Z

data/raw/oshwhub/48dd1b650d084739bef92ab8a651975a/metadata.json

@@ -0,0 +1,40 @@
+{
+  "source": "oshwhub",
+  "source_url": "https://oshwhub.com/wzw666/ip5389",
+  "project_id": "48dd1b650d084739bef92ab8a651975a",
+  "title": "IP5389[100瓦双向快充移动电源方案]",
+  "description_short": "100瓦双向快充移动电源方案",
+  "description_path": "description.md",
+  "author": {
+    "username": "wzw666",
+    "display_name": "小煜哥哥",
+    "user_id": "67f4ab719a2a4182934deee8cc979e93"
+  },
+  "license": "CC-BY-NC-SA 3.0",
+  "tags": [],
+  "created_at": "2021-09-09T10:36:14.000Z",
+  "updated_at": "2026-04-15T05:31:09.000Z",
+  "published_at": "2022-09-13T01:15:55.000Z",
+  "crawled_at": "2026-04-28T17:28:24.081470+00:00",
+  "metrics": {
+    "likes": 368,
+    "stars": 778,
+    "forks": 341,
+    "views": 121491,
+    "watch": 0,
+    "comments": 205
+  },
+  "cover": {
+    "url": "https://image.lceda.cn/avatars/2021/10/GzDiNwDZSinZ1pfr44sY5cLLFIK0CGAKHSMmMJkK.png",
+    "path": null
+  },
+  "files": [],
+  "raw_fields": {
+    "path": "wzw666/ip5389",
+    "grade": 3,
+    "origin": "std",
+    "public": true,
+    "publish": true,
+    "skipped_files": []
+  }
+}