company show: drop payment_configs GET entirely

[DamoneMX]

Summary

• gusto company show was firing GET /v1/companies/{uuid}/payment_configs
  in parallel with the primary company GET. The endpoint gates on an active
  PartnerCompanyMapping, which gusto auth login doesn't create, so the
  call always 404s with CanCan::AccessDenied for the companies this CLI
  currently serves. The CLI suppressed the 404 client-side, so the failure
  was invisible to users but still hit Embedded Pay's error dashboards. Over
  the last 8d, 27 invocations, 100% errors.
• Remove the call unconditionally rather than gate it on
  is_partner_managed. Alongside the GET:
  • drop payment_config from the --agent JSON envelope and
    payment_speed from summary
  • drop the Payment speed line from human-readable output
  • drop the PaymentConfig type and is_partner_managed from the
    internal CompanyRecord type
  • move company_payment_configs:read from REQUIRED_SCOPES to
    DROPPED_SCOPES (no in-surface command needs it now)
• Reduce parallel GETs from three to two (/v1/companies/{uuid} and
  /v1/companies/{uuid}/pay_schedules). Breaking change to the --agent
  JSON envelope shape.

Test plan

• bun run typecheck, bun run lint, bun run format:check pass
• bun test src/commands/company src/lib/oauth → 76 pass / 0 fail. The
  network test asserts the /payment_configs endpoint is never called
  using an anchored regex (/companies/[^/]+/payment_configs(?:$|\?)/).
• Full bun test → 1134/1135. The one failure
  (--check exits 0 when NOTICES is current) is pre-existing on
  origin/main, unrelated to this change (drift from other PRs merged
  today, verified by running the script from a clean origin/main
  checkout).
• bun run build compiles clean.
• Live sandbox run against a non-partner-managed company: 2 GETs on the
  wire (/v1/companies/{uuid}, /v1/companies/{uuid}/pay_schedules);
  envelope shape validated by unit tests (no payment_config, no
  summary.payment_speed).

[ashieh]

I am thinking we should remove the ability to GET payment configs. I don't think we will have partner-managed companies going through this flow but should get confirmation from Cathy Slack

[ashieh]

Code looks good. I think we should drop the reference to AINT-786 in the PR title.