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/104/01_scmp-com.txt

@@ -0,0 +1,19 @@
+Hong Kong police rescue cryptocurrency trader kidnapped by triad gang who demanded HK$30 million ransom | South China Morning Post
+
+Hong Kong police rescue cryptocurrency trader kidnapped by triad gang who demanded HK$30 million ransom
+
+The victim, 39, was lured into Kowloon Bay industrial unit on November 6 to carry out cryptocurrency transaction
+
+He refused to arrange payment of HK$30 million ransom and officers rescued him six days later, while manhunt is under way for at least eight others
+
+Published: 6:32pm, 14 Nov 2021Updated: 11:27pm, 14 Nov 2021
+
+Police have made a dramatic rescue of a cryptocurrency trader who was kidnapped by suspected triad members and held at a house in northern Hong Kong for nearly a week as his captors tried to extract a HK$30 million (US$3.85 million) ransom from his family.
+
+Police raided the residence in the New Territories after being contacted by the family, and just as officers were swooping on the location, the trader managed to climb out a window and drop to the ground, the force revealed on Sunday.
+
+But the kidnappers had beaten the victim, 39, with hammers in their unsuccessful attempt to force the ransom payment and he suffered leg fractures requiring hospital treatment, a source told the Post.
+
+Officers arrested seven people and were hunting for about eight others, believed to be members of a Sun Yee On triad faction, including the suspected division boss.
+
+Authorities were investigating whether any money was stolen from the man as he was forced to reveal the passwords for his bank and cryptocurrency accounts, acting Senior Superintendent Alan Chung of the Kowloon West regional crime unit said. According to the source, the digital currency holdings were worth more than HK$20 million.

merge-output/staging/104/index.json

@@ -0,0 +1,16 @@
+[
+  {
+    "case": 104,
+    "n": 1,
+    "field": "url",
+    "url": "https://www.scmp.com/news/hong-kong/law-and-crime/article/3156021/hong-kong-police-hunt-triad-gang-members-who-kidnapped",
+    "host": "scmp.com",
+    "fetched_at": "2026-09-05T12:53:03+00:00",
+    "verdict": "FETCHED",
+    "method": "raw",
+    "http": 200,
+    "chars": 1755,
+    "sha256": "2415fd6144e5d257c152cf5a20084df8ca1a7fefc96409cfada8564536e63721",
+    "final_url": null
+  }
+]