feat(sources): fetch linked URLs for the 252 spreadsheet-only cases

Until now only cases 357+ (plus a few older ones) had their linked URLs
fetched; the other 252 dossiers held just the text pasted into the
spreadsheet, often only the lede. This pass fetches every linked URL for
those cases so the full text is on file before link rot takes it.

- stage_all.py: new --include-sheet-cases flag that lifts the skip on
  cases holding spreadsheet articles. Resumable as before.
- staging/: raw extracts and index.json for the 252 cases.
- sourced-articles.json, case-files-manifest.json: 188 new UNTRIMMED
  blocks. 179 cases gained at least one fetched article; 73 got none
  (49 BLOCKED, 18 THIN, 9 DEAD, 4 video/social, 3 ERROR).
- sources/*.txt: rebuilt with build_cases.py --all. Sheet pastes are
  kept; fetched blocks sit beside them under the NOT YET TRIMMED banner.
  Files previously committed with CRLF are now LF.
- wayback-availability.json: Wayback snapshots exist for 73 of the 98
  failed URL slots; input for an archive-fetch pass.
- README-START-HERE.md: progress note and next step.

verify_all.py PASSES (1836 checks).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GZZENdTLzNGsbNy4DyF1yt

merge-output/staging/027/01_scmp-com.txt

@@ -0,0 +1,21 @@
+Hong Kong bitcoin trader lured to bogus meeting and robbed of HK$1.4 million | South China Morning Post
+
+Hong Kong bitcoin trader lured to bogus meeting and robbed of HK$1.4 million
+
+Police are searching for five men, two who posed as sellers and three who attacked victim and took his bag
+
+Published: 1:30pm, 19 Jan 2018Updated: 11:05pm, 6 Feb 2018
+
+A citywide police search was under way on Friday for five men after a local bitcoin trader was lured to a bogus business meeting and robbed of HK$1.4 million (US$180,000) on a busy street in Hong Kong.
+
+The five included two suspects who posed as sellers and arranged to meet the victim to trade bitcoin for cash, according to a police source.
+
+“The other three attacked the victim and took his bag, containing cash and a mobile phone,” he said.
+
+The attack happened in North Point, on Hong Kong Island.
+
+As of just before noon on Friday, the five suspects were still on the run, according to police.
+
+Did bitcoin just burst? How the cryptocurrency slump compares to history’s biggest fads
+
+The victim is a 34-year-old Hong Kong man surnamed Lee, who was contacted via his WeChat account on Thursday morning. He was asked to go to the Starbucks outlet on Hennessy Road, Wan Chai for a business meeting at 4.30pm.

merge-output/staging/027/index.json

@@ -0,0 +1,16 @@
+[
+  {
+    "case": 27,
+    "n": 1,
+    "field": "url",
+    "url": "https://www.scmp.com/news/hong-kong/law-crime/article/2129665/hong-kong-bitcoin-trader-lured-bogus-meeting-and-robbed",
+    "host": "scmp.com",
+    "fetched_at": "2026-09-05T12:56:12+00:00",
+    "verdict": "FETCHED",
+    "method": "raw",
+    "http": 200,
+    "chars": 1263,
+    "sha256": "e853e0ab2995d291e02f2329ef41c348f3678f82ec05474a3dbce99879af7bca",
+    "final_url": null
+  }
+]