docs: fix stale receiver references in README and CLAUDE.md

[ericviana]

Summary

This CLI's command surface was already fully migrated from receivers to customers in code and tests (customers list/get/create/update/delete/limits/limits_increase_requests/create_limit_increase/rfi_get/rfi_submit, --customer-id flags, /customers paths). README.md and this repo's CLAUDE.md had not been updated to match and still documented the old receivers commands, --receiver-id flags, and /receivers paths.

This matters beyond cosmetics because CLAUDE.md is fed directly to the automated .github/workflows/api-sync.yml Claude-driven sync job as its pattern reference. The stale submitReceiverRfi/receivers/${receiverId}/rfi worked example risked teaching that job the wrong naming convention on its next run.

What changed

• README.md: renamed the "Receivers" section to "Customers" with the accurate command list (including limits, limits_increase_requests, create_limit_increase, rfi_get, rfi_submit, none of which were documented before at all), and fixed --receiver-id -> --customer-id in the Bank Accounts, Blockchain Wallets, Virtual Accounts and Offramp Wallets sections.
• CLAUDE.md: fixed the naming-convention example, the path-params guidance, the API-path-to-command naming table, the worked "dynamic request body" example (submitCustomerRfi/customerId//customers/${customerId}/rfi), and the test-placement example, all of which referenced receivers/receiverId instead of the shipped customers/customerId.
• package.json: version bump 0.4.0 -> 0.5.0 (minor, since this is an additive/non-breaking docs fix).

Why this is safe today

Every change in this PR is documentation only, no source or test files changed. It does not touch any of the still-in-progress wave-2 renames:

• transfer_quotes create (--receiver-wallet-address/--receiver-token/--receiver-network) and tos initiate (--receiver-id) still send receiver_wallet_address/receiver_token/receiver_network/receiver_id on the wire, deliberately unchanged, because the currently deployed API has no customer_* equivalent for those fields yet (only PR #1799 in blindpay-v2, not yet deployed, adds them).
• receiver_amount/sender_amount on quotes and transfers are untouched, confirmed present at src/commands/resources.ts:500,528,531,1032 and src/__tests__/resources.test.ts:461. That field is intentionally never renamed (it means "amount the receiving side gets," not a reference to the customer resource).

This CLI has no webhook event enum/constant anywhere in source (createWebhookEndpoint only ever posts {url, description}, no --events flag exists), so there was nothing to add customer.new/customer.update/customer.delete to and nothing receiver.* to deprecate. Likewise there is no legacy receivers resource, no RECEIVERS_* error codes, and no receiver_id/customer_id translation shim in this repo to remove. Confirmed by full-repo grep before making any change.

Build output

$ bun install --frozen-lockfile
12 packages installed [33.00ms]

$ bun run typecheck
$ tsc --noEmit
(clean)

$ bun run lint
$ oxlint -c oxlint.json src/
Found 0 warnings and 0 errors.
Finished in 7ms on 7 files with 100 rules using 10 threads.

$ bun test
108 pass
0 fail
196 expect() calls
Ran 108 tests across 4 files. [179.00ms]

$ bun run build
Bundled 20 modules in 9ms
  index.js  122.95 KB  (entry point)

Test plan

• bun install --frozen-lockfile && bun run typecheck && bun run lint && bun test && bun run build all pass
• Verified every receiver_amount/sender_amount exempt occurrence is untouched
• Verified the wave-2 receiver_* wire fields in transfer_quotes create and tos initiate are untouched

https://claude.ai/code/session_01F1stiNzuNtJXoXtiW9ZCbs