[haimbj1]

TL;DR
No tutorial shows a full confidential token transfer from start to end. New developers cannot see how little code CoFHE needs.
Add one tutorial page with a project that CI tests. Alice pays Bob, Bob reads his balance, and Eve cannot.

Jira: DOC-77. Stacked on #126: merge that first, then this PR moves to main.

What

• A new page, cofhe/tutorials/confidential-payment: Alice pays Bob 100 tokens. Bob reads his balance, and Eve cannot.
• A complete Hardhat project at cofhe/tutorials/examples/confidential-transfer/:
  • a short FHERC20 token
  • a test on local mocks
  • a Sepolia script
• Readers download the project with npx degit FhenixProtocol/fhenix-docs/cofhe/tutorials/examples/confidential-transfer.
• The page is the first tutorial in the nav and in the Tutorials overview.

How the page stays correct

• New workflow Tutorial examples. It runs npm ci && npm test in every example project from a clean checkout.
• New check check-example-regions.py. Each code block on the page has an invisible marker naming a region in a project file. The check fails if the block and the region differ. So the code on the page is the code CI tested.
• check-versions.py now also checks the example's package.json pins against the compatibility page.

Checks

• npm ci && npm test from a clean copy: 2 passing.
• Region check: 0 errors. Its self-test passes 6 of 6.
• A wrong pin in the example makes check-versions --docs fail. With the pin restored, it passes.
• The page's Solidity compiles against the pinned contracts.
• Structure linter: 0 errors. Vale: 0 errors.
• mint validate and mint broken-links --check-anchors --check-redirects pass.

Sepolia run (2026-10-20)

npm run sepolia passed, with only Alice's key. Bob was a fresh random wallet.

• Token: https://sepolia.etherscan.io/address/0x93B0a6533276590A1d25bbfba49228fDeaCFF3C9
• Transfer: https://sepolia.etherscan.io/tx/0xc265d13901aee91f89c5c81bce3ae72cd9a62c97e0e026fcdc3c8479eda024aa
• Output: Bob's balance: 100, Alice's balance: 900

Gas on Sepolia, 1.0.0 (not in this PR)

Action	Measured	"Gas and benchmarks" page
confidentialTransfer to a new holder	1,360,076	474,400
confidentialTransfer to an existing holder	1,142,202	421,500
confidentialTransferFrom by an operator	1,145,233	424,800
setOperator	128,680	46,700

setOperator runs no FHE and writes one storage slot, but it also costs 2.75 times the page value. So the gap does not come from 1.0.0. Sepolia's gas pricing has changed since the page was measured. The page needs a separate decision: which network it describes, and a new measurement.