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/sources/083_F-T.txt

@@ -77,6 +77,38 @@ The case is being handled by Prosecutor's Office No. 19 of Police Station 35.
 
 
 
+------------------------------------------------------------------------------------------------
+FETCHED ARTICLE 1  [RAW EXTRACT — NOT YET TRIMMED]
+  !! This is the whole page as extracted. It still contains site furniture,
+  !! and may contain teaser headlines for UNRELATED cases. Trim on read-through.
+  !! Do not quote from it without checking the passage belongs to this case.
+  Source     mendovoz.com
+  URL        https://www.mendovoz.com/actualidad/policiales/2021/3/19/le-robaron-350-mil-un-joven-en-guaymallen-98425.html
+  Field      url
+  Retrieved  2026-09-05T12:53:56+00:00 via raw HTTP retrieval, deterministic extraction (HTTP 200)
+  Language   unknown
+  Kept       paragraphs ALL 6 paragraphs, untrimmed
+  Length     730 chars
+  Integrity  sha256 3d6277b9ef36208f488698136ca7812600b0659aa566b32a79f8e6332e26e414
+  Trimmed    NOT TRIMMED. Full page extract; trim on read-through.
+  Caveat     retrieved from a live page on the date above. Unlike text copied
+             from the spreadsheet, there is no second copy to hash it against.
+------------------------------------------------------------------------------------------------
+
+ORIGINAL (unknown, verbatim as retrieved)
+
+Le robaron $350 mil a un joven en Guaymallén | MendoVoz
+
+Los delincuentes sorprendieron al joven cuando este había pactado la venta de bitcoin.
+
+Este jueves, un joven de 26 años fue víctima del delito y del engaño. El hecho ocurrió cerca de las 19.30 en la calle 2 de Mayo y Severo del Castillo del departamento de Guaymallén.
+
+El robo se produjo cuando el hombre se dirigía al lugar para venderle a unas personas la moneda virtual bitcoin y en un momento unos delincuentes lo sorprendieron y le sustrajeron un iPhone, 120 mil pesos y 2500 dólares.
+
+Horas más tarde, personal policial en encontró el iPhone entre las malezas de un descampado de la calle Reconquista
+
+Intervino en el caso la Oficina Fiscal N°19 de la Comisaría 35°
+
 ================================================================================================
 generated from attacks-export-Gart-website.json + reported_K&R  |  case 083
 ================================================================================================