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/050/01_the-independent-com.txt

@@ -0,0 +1,31 @@
+Bitcoin trader brutally tortured with drill in cryptocurrency robbery | The Independent | The Independent
+
+Please refresh the page or navigate to another page on the site to be automatically logged inPlease refresh your browser to be logged in
+
+Police in the Netherlands are investigating the brutal torture of a bitcoin trader, whose home was raided by criminals looking for cryptocurrency.
+
+Three robbers disguised as police entered the victim's home in Drenthe and attacked him with a drill in front of his four-year-old daughter, Dutch publication De Telegraaf reported.
+
+The hour-long ordeal also involved the victim being threatened with firearms, before the perpetrators fled in an escape vehicle. The digital nature of bitcoin and other cryptocurrencies mean long and complex passwords – or private keys – are required to access assets and transfer them to another digital wallet.
+
+Police did not reveal the identity of the victim but it is not believed any cryptocurrency was stolen during the raid.
+
+A spokesperson for Northern Netherlands Police told The Independent that the investigation is ongoing.
+
+It is not the first time criminals have targeted cryptocurrency investors and traders, with the earliest reported instance taking place in 2015.
+
+In February of that year, New York City firefighter Dwayne Richards was stabbed in Willamsburg, Brooklyn, by muggers who demanded he transferred bitcoin to their digital wallets.
+
+Cryptocurrency mystery deepens as $143m goes missing
+
+Bitcoin, which is currently worth around $3,800 (£2,800), is semi-anonymous and therefore difficult to trace to a single individual.
+
+Since its peak in late 2017, bitcoin has lost close to three quarters of its value, yet still remains an attractive prospect for criminals.
+
+In one of the most notable examples of criminals targeting holders of bitcoin, kidnappers in the Ukraine made more than $1 million in digital currency in 2017 after ransoming cryptocurrency analyst Pavel Lerner.
+
+The UK's first bitcoin heist took place in January last year, when armed robbers broke into the home of cryptocurrency trader Danny Aston in Moulsford, South Oxfordshire.
+
+Mr Aston was tied up during the home invasion and an unknown quantity of bitcoin was seized by the attackers.
+
+Join thought-provoking conversations, follow other Independent readers and see their replies

merge-output/staging/050/index.json

@@ -0,0 +1,16 @@
+[
+  {
+    "case": 50,
+    "n": 1,
+    "field": "url",
+    "url": "https://www.the-independent.com/tech/bitcoin-robbery-torture-cryptocurrency-netherlands-a8807986.html",
+    "host": "the-independent.com",
+    "fetched_at": "2026-09-05T12:55:00+00:00",
+    "verdict": "FETCHED",
+    "method": "raw",
+    "http": 200,
+    "chars": 2357,
+    "sha256": "68e352faaf95afe530ef631f701f8c57f9966f5c8f1073326f33019cdf137194",
+    "final_url": null
+  }
+]