data(wallets): add optional extensionBrowsers column, seed MetaMask and Phantom from first-party docs (DBIP #3713) - #3741

Closes #3713 (data side)

Problem

No dedicated field records which desktop browsers a provider officially supports for its wallet extension; supportedPlatforms only describes delivery formats.

Changes

• Appended the extensionBrowsers column to all 92 wallet tables: references/offers/wallets.csv (canonical, 106 rows) + 91 listings/specific-networks/*/wallets.csv.
• Seeded only the two evidence-backed canonical rows (first-party docs checked 2026-09-08):
  • metamask → ["Brave","Chrome","Edge","Firefox","Opera"] (MetaMask FAQ)
  • phantom → ["Chrome"] (Phantom supported platforms and browsers; Firefox no longer receives updates, other Chromium browsers can run the extension but are not officially supported)
• All other canonical cells and all network listing cells left blank (unknown → existing inheritance rules apply). No values derived from Web / Browser Extension platform entries.
• The two legacy listing cells containing browser names (stellar/freighter, algorand/lute in supportedPlatforms) are left untouched — per DBIP [DBIP] Add evidence-backed desktop extension browser support to wallets #3713 §Migration 4 the old cells alone are not evidence, and that cleanup belongs to data(wallets): normalize supportedPlatforms to the DBIP-3243 controlled vocabulary (Closes #3243) #3670.

Verification

• All 92 files rectangular: 22 → 23 columns, CRLF line endings preserved
• Only the two seeded cells are non-empty; both parse to the documented arrays
• validate_csv.py → csv_to_json.py → validate.py all green locally
• Generated network JSON inherits the canonical values (e.g. ethereum.json metamask carries the full array) and columns.wallets order includes extensionBrowsers
• Schema/validator side lives in the paired tools PR (base json-tools); CI on this PR will stay red until that lands, matching the [DBIP] Add per-variable types for required self-hosted MCP configuration #3683/feat(mcpservers): selfHostedEnvVarTypes schema, column metadata and validation (DBIP #3683) #3698+feat(mcpservers): add selfHostedEnvVarTypes column, classify Filecoin Onchain Cloud PRIVATE_KEY (DBIP #3683) #3699 pattern

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