feat(resource-server): wire optional paywall into the example host

[levalleux-ludo]

Summary

• createResourceServerApp now accepts optional paywall (PaywallProvider) and paywallConfig, forwarded to the underlying expressMiddleware and mountX402b calls.
• New env vars (PAYWALL_APP_NAME, PAYWALL_WALLETCONNECT_PROJECT_ID, PAYWALL_TESTNET) populate a paywall block on the parsed env; setting any of them opts in.
• src/index.ts's reference assembly comment now shows how a fork wires in evmEscrowPaywall alongside the exchangeReader.
• Two new tests verify the wiring through both expressMiddleware (GET /resource) and mountX402b (POST /x402B/commit) using a stub PaywallProvider. End-to-end coverage against the real evmEscrowPaywall lives one PR up in @bosonprotocol/x402-server-express's own suite.

Why this completes the staged rollout

This is the fourth and final PR in the browser-paywall sequence:

1. feat: add initial implementation of x402-client-browser with tests and docs #77 `@bosonprotocol/x402-client-browser` — viem WalletClient / EIP-1193 → Signer adapters
2. feat: add @bosonprotocol/x402-paywall package #78 `@bosonprotocol/x402-paywall` — React+wagmi paywall bundle + `generateHtml` server entry
3. feat(server-express): add paywall + paywallConfig options #79 `@bosonprotocol/x402-server-express` — `paywall:` option + Accept content negotiation
4. feat(resource-server): wire optional paywall into the example host #80 (this PR) — example host wiring; fork `src/index.ts`, set `PAYWALL_*` env vars, browse to `/resource` and see the paywall

Drive-by fix

Widens `PaywallConfigLike` in `@bosonprotocol/x402-server-express` from `Record<string, unknown>` to `object` so concrete `PaywallConfig` shapes (with named optional fields, no index signature) satisfy it structurally. Required for this example to typecheck without casts; the structural-typing intent of `PaywallProviderLike` was already documented in #79.

Notes

• Depends on feat(server-express): add paywall + paywallConfig options #79 (`server-express` paywall option); base is set accordingly. Auto-rebases to `main` once feat: add initial implementation of x402-client-browser with tests and docs #77 → feat: add @bosonprotocol/x402-paywall package #78 → feat(server-express): add paywall + paywallConfig options #79 merge.
• The binary still refuses to start without an `ExchangeReader` (unchanged) — the paywall integration is for the programmatic / fork path, plus the test surface.

Test plan

• `pnpm --filter @bosonprotocol/x402-example-resource-server build` — clean
• `pnpm --filter @bosonprotocol/x402-example-resource-server test` — 14/14 (11 existing + 3 new)
• Repo-wide `pnpm build` — 16/16 successful
• Repo-wide `pnpm test` — 32/32 successful
• Repo-wide `pnpm lint` — 16/16 successful
• Repo-wide `pnpm format:check` — clean
• Manual browser smoke test — needs a forked binary with `ExchangeReader` wired in and a live facilitator; deferred to your local environment.

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[Copilot]

Pull request overview

This PR wires an optional HTML paywall (via @bosonprotocol/x402-paywall) into the resource-server example host, forwarding paywall/paywallConfig through to @bosonprotocol/x402-server-express so browser clients can receive HTML 402 challenges while programmatic clients keep receiving JSON.

Changes:

• Extend createResourceServerApp to accept optional paywall + paywallConfig and forward them into both expressMiddleware and mountX402b.
• Add PAYWALL_* env parsing to produce a paywall config block and document it in the example README and index.ts fork guidance.
• Add tests that validate the paywall wiring for both GET /resource and POST /x402B/commit, and widen PaywallConfigLike in server-express to accept concrete PaywallConfig shapes.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
typescript/packages/server-express/src/internal/x402-challenge.ts	Widens PaywallConfigLike to object to support structurally-typed concrete configs.
pnpm-lock.yaml	Adds workspace link for @bosonprotocol/x402-paywall in the example’s deps.
examples/resource-server/test/resource-server.test.ts	Adds tests validating HTML/JSON 402 behavior and wiring through both middleware surfaces.
examples/resource-server/src/index.ts	Updates fork/reference assembly comment to show paywall provider wiring.
examples/resource-server/src/config.ts	Parses PAYWALL_* env vars into an optional env.paywall config block.
examples/resource-server/src/app.ts	Adds optional paywall + paywallConfig options and forwards them to server-express adapters.
examples/resource-server/README.md	Documents new PAYWALL_* env vars and browser paywall behavior.
examples/resource-server/package.json	Adds @bosonprotocol/x402-paywall dependency.
.changeset/resource-server-example-paywall.md	Declares version bumps and summarizes the feature + type change.

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

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