Add x402/MPP RPC micropayments to build-web3's Quicknode references, and retire Marketplace terminology

[0xsergen]

Updates the Quicknode CLI and SDK references in build-web3 for the paid RPC lane shipped in qn 0.6.0 / @quicknode/sdk 3.8.0, and brings add-on naming and links in line with the current public catalog.

Linear: CON-891 (add-on rebrand follows CON-890 / CON-884)

Commits

1. Add x402/MPP micropayment coverage to Quicknode CLI and SDK references — the substance of CON-891.
2. Replace Marketplace terminology with Add-ons — Quicknode no longer uses the "Marketplace" name.
3. Use current catalog names for the Risk Assessment and GoldRush add-ons.

x402/MPP coverage

• references/quicknode/cli-reference.md: new Paid RPC (x402 and MPP) section covering the four payment paths (--x402, --mpp, --x402-drawdown, --mpp-session), qn wallet key handling and precedence, supported-payments discovery, the [rpc.payment] config block, and retry/exit-code semantics — including that exit 3 means the outcome is unknown and the wallet may already have been charged. The confirmation-behavior section now names the newly gated commands.
• references/quicknode/sdk-reference.md: new RPC Micropayments section covering the keyless rpc.payment config, per-request calls, callWithReceipt, generatePaymentWallet, the x402 credit-drawdown flow, MPP payment channels, the Rust payment feature flags, and the payment error types.
• references/quicknode/x402-reference.md, references/quicknode/mpp-reference.md, references/agent-access-and-automation.md: point at the CLI and SDK lanes as the fastest path.
• references/quicknode-products.md, PRODUCT_CATALOG.md: note the SDK/CLI RPC lane; canonicalize /docs/quicknode-cli and /docs/quicknode-sdk to /docs/cli and /docs/sdk.
• Plugin version bumped to 1.0.1 across the Claude, Cursor, and Codex manifests.

Every command surface, flag, version floor, and payment gateway response in these sections was checked against the installed qn 0.6.0 and the live x402/MPP gateways rather than taken from the docs. Two upstream doc discrepancies were deliberately not propagated, because our examples already match the shipped CLI: /docs/cli shows qn sql query --cluster (actual flag is --cluster-id), and /docs/cli/examples shows flag-style arguments for endpoint tag add, endpoint tag rename, security referrer add, security ip add, and a request-filter add subcommand (actual: positional arguments, and request-filter create).

Add-ons rebrand

• Renamed references/marketplace-addons.md to references/addons.md and updated the inbound links in SKILL.md, references/quicknode-provider.md, and references/quicknode/rpc-reference.md.
• Repointed every marketplace.quicknode.com/add-on/<slug> link at www.quicknode.com/add-ons/<slug>, and replaced the stale yellowstone-grpc-geyser-plugin slug with solana-grpc-geyser-plugin.
• Relabelled **Marketplace:** links as **Add-on page:**, the product-group row as "Endpoint Add-ons", and the doc-link entries accordingly.
• Metaplex DAS API and Blockbook are now described as standalone products rather than add-ons; Solana gRPC and Ordinals & Runes keep add-on wording, since both still have live add-on pages.
• Added the (previously missing) add-on pages for the Solana Priority Fee API and Jito Bundles sections.
• Add-on names now match the catalog: Risk Assessment API (was Scorechain Risk Assessment API) and GoldRush Multichain Data APIs (was Covalent GoldRush Wallet/Data APIs).

All 15 add-on URLs were verified against the live catalog by page title rather than status code — www.quicknode.com/add-ons/<slug> returns HTTP 200 even for slugs that no longer exist, so checking status codes would have passed dead links. Two slugs had changed and are corrected here: Priority Fee is solana-priority-fee, and Jito is lil-jit-jito-bundles-and-transactions. Every relative markdown link in the skill was also confirmed to resolve.

A matching PR keeps quicknode-skill in parallel: quiknode-labs/blockchain-skills#25