data(filecoin): add Forest Explorer USDFC faucet

[EazyHood]

Summary

• add the canonical Forest Explorer USDFC faucet offer from ChainSafe
• list it for Filecoin Calibration through an !offer: reference
• reuse the existing ChainSafe provider and calibnet chain assets
• keep the contribution to two new rows and 13 non-null cells

Official evidence

• Filecoin's Calibration documentation lists the ChainSafe Calibration USDFC faucet: https://docs.filecoin.io/networks-and-tools/networks/calibration
• Filecoin's official Filecoin Pin tutorial directs builders to the same faucet for test USDFC: https://docs.filecoin.io/builder-cookbook/filecoin-pin/dapp-demo
• ChainSafe's Forest Explorer source identifies the page as the Filecoin Calibnet USDFC Faucet: https://github.com/ChainSafe/forest-explorer/blob/main/src/faucet/views/faucets/calibnet_usdfc.rs

The faucet URL is live behind a Cloudflare browser challenge (HTTP 403 to automated HEAD requests), and both official Filecoin sources above link to it.

Collision audit

• searched current main and open PRs for both new slugs and the exact faucet URL; no match
• related PRs data: document ChainSafe Filecoin faucet limits #2588, Add Forest Calibration faucet for Filecoin #2915 and Add Forest Explorer Faucet for Filecoin mainnet and calibnetAdd forest filecoin faucet #3011 cover Forest/ChainSafe tFIL faucets, not USDFC
• data: add Plumbline Filecoin Calibration faucets #3126 covers a different USDFC faucet from Plumbline at a different URL
• repeated the search immediately before publication

Validation

• official json-tools validate_csv.py: All checks passed
• official csv_to_json.py generation: passed
• official validate.py schema validation for all generated network JSON: passed
• offer/listing widths: 13/14 columns
• git diff --check: passed

Rewards address

0x06f44f4839fd5df4f4670036d028b29dec939363

[github-actions]

Summary

Status	Count
🔍 Total	2
🔗 Unique	2
✅ Successful	2
⏳ Timeouts	0
🔀 Redirected	0
👻 Excluded	0
❓ Unknown	0
🚫 Errors	0
⛔ Unsupported	0

Full Github Actions output

[USS-Supervisor]

Verdict: COMMENT
Risk: LOW
Summary: I did not find a data-integrity issue in this change. The new Forest Explorer USDFC faucet offer and Filecoin Calibration listing keep the CSV widths stable, use unique slugs, resolve the !offer:forest-usdfc-faucet reference, and match the cited Filecoin/ChainSafe evidence.
Findings: None. Approval is blocked in this review cycle because the only successful link-check run for the current head started at 2026-08-23 13:01 UTC, before this 14:53 UTC review cycle; under the current approval rule I cannot approve without a current-cycle link-check=success.
Confidence: HIGH