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/186/01_asianews-network.txt

@@ -0,0 +1,15 @@
+Hunt for Chinese gang suspected of THB70 million robbery in Thailand’s – Asia News Network
+
+BANGKOK – Pathum Thani police on Wednesday launched a hunt for a gang of four Chinese nationals following an armed robbery at a luxury house located on a golf course in Muang district of Pathum Thani province.
+
+Ke Jibao, 34, a Chinese businessman, told officers of Pak Klong Rangsit police station that four armed men of Chinese nationality wearing ski masks barged into the house on Tuesday night.
+
+The intruders captured the residents, comprising three men and three women, and forced Ke to transfer US$2 million (70 million baht) of digital money to their account, he said.
+
+The victim said after his relatives in China had completed the transfer, the four grabbed the house’s CCTV servers and drove away in his black Toyota Alphard, licence plate 1ขย 9302 Bangkok, at around 2.45am.
+
+Ke sustained a knife wound to his wrist during the attack, while another resident was hit on the forehead with a gun. They were sent to a hospital for treatment after being questioned by the police.
+
+On Wednesday afternoon, police found the car abandoned near a power plant in Ban Mai subdistrict, and are conducting a thorough forensic investigation in the hope of finding traces of the thieves.
+
+Pak Klong Rangsit station chief Pol Col Narong Iamrahong said he would lead the investigation himself, adding officers are questioning each of the victims and neighbours, as well as checking CCTV footage in nearby areas to track the gang’s escape route.

merge-output/staging/186/index.json

@@ -0,0 +1,16 @@
+[
+  {
+    "case": 186,
+    "n": 1,
+    "field": "url",
+    "url": "https://asianews.network/hunt-for-chinese-gang-suspected-of-thb70-million-robbery-in-thailands/",
+    "host": "asianews.network",
+    "fetched_at": "2026-09-05T12:50:14+00:00",
+    "verdict": "FETCHED",
+    "method": "raw",
+    "http": 200,
+    "chars": 1531,
+    "sha256": "1592d76b1e07ceab9ca9976387b4a7d6a3d025b293afb145765f2d33e69d79d7",
+    "final_url": null
+  }
+]