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/216/01_vietnamnet-vn.txt

@@ -0,0 +1,43 @@
+Ho Chi Minh City police bust Chinese-led kidnapping gang, rescue victim safely
+
+© Copyright of Vietnamnet Global.
+
+Vietnamese police have arrested a group of Chinese and Vietnamese criminals for kidnapping a Chinese national and demanding a $400,000 ransom in cryptocurrency. The victim was safely rescued in a tactical police raid.
+
+On March 6, the Ho Chi Minh City Police Department confirmed that they had arrested five suspects on charges of illegal detention.
+
+Ma Cai (49), Fan GuoHui (39), and Li Chuang (47) – all Chinese nationals.
+
+Le Thi Bich Xuyen (35, from Can Tho) and Huynh Van Toan (30, from Binh Dinh) – Vietnamese nationals.
+
+Another Vietnamese suspect, Nguyen Thanh Vu (31, from Binh Dinh), was also arrested for illegal detention.
+
+At 6 AM on February 28, Ho Chi Minh City’s Criminal Police Department received a report about a kidnapping and ransom case involving Chinese suspects with assistance from Vietnamese accomplices.
+
+The city’s police force, under the direction of the Ministry of Public Security, launched an immediate investigation.
+
+Using advanced tracking techniques and intelligence from local informants, authorities identified six suspects and located their hideout in Pham Van Hai commune, Binh Chanh district. The location was remote, heavily wooded, and far from residential areas, making it a strategic hideout for the gang.
+
+Due to concerns that the kidnappers were armed and dangerous, police devised a tactical raid plan.
+
+After careful preparation, officers launched a surprise raid, successfully arresting all suspects and rescuing the hostage unharmed.
+
+At the police station, the suspects confessed to the crime.
+
+According to their statements, the three Chinese masterminds - Ma Cai, Fan GuoHui, and Li Chuang - devised the kidnapping scheme to extort money from the victim.
+
+They demanded a ransom of 600,000 USDT (a cryptocurrency equivalent to 10 billion VND).
+
+Since they were unfamiliar with Vietnam’s geography, they hired local Vietnamese accomplices to monitor the victim’s movements. The Vietnamese gang members were paid tens of millions of dong for their assistance.
+
+In the early hours of February 28, as soon as the victim stepped out of a car, Fan GuoHui and the Vietnamese accomplices ambushed him, forcing him into another vehicle. Ma Cai and Li Chuang followed on motorcycles to keep watch.
+
+The victim was taken to an isolated location, where the gang threatened him and demanded the ransom. However, their plan was foiled by the swift action of the police.
+
+The case is still under further investigation, with authorities working to determine if more individuals were involved in the criminal operation.
+
+Former police officer detained, stripped of title after kidnapping child
+
+Vietnamese man arrested for kidnapping boy in Hanoi
+
+Vietnamese Embassy in Mexico assists 11 citizens after kidnapping

merge-output/staging/216/index.json

@@ -0,0 +1,16 @@
+[
+  {
+    "case": 216,
+    "n": 1,
+    "field": "url",
+    "url": "https://vietnamnet.vn/en/ho-chi-minh-city-police-bust-chinese-led-kidnapping-gang-rescue-victim-safely-2378098.html",
+    "host": "vietnamnet.vn",
+    "fetched_at": "2026-09-05T12:48:25+00:00",
+    "verdict": "FETCHED",
+    "method": "raw",
+    "http": 200,
+    "chars": 2865,
+    "sha256": "1a7d8b179359406e43fa71d87630362484fed1d2ff4444cedabb9001f2b10150",
+    "final_url": null
+  }
+]