docs(transactions): document the 501 response on the cancel endpoint

[ls-bolt]

Summary

• POST /transactions/{transactionId}/cancel returns 501 NOT_IMPLEMENTED for any payment rail whose banking partner exposes no cancellation facility, but the spec never documented a 501 response. Integrators hit an undocumented status on the endpoint's primary path.
• Adds the 501 response (Error501, already used by /cards, /customers, and /platform/config).
• Rewrites the 200 description: a success means the banking partner accepted the cancellation request, not that the transfer is already cancelled. The partner confirms asynchronously, so the transaction body returned may still report its pre-cancellation status.

Changes: 3 files

• openapi/paths/transactions/transactions_{transactionId}_cancel.yaml — add 501, clarify 200
• openapi.yaml, mintlify/openapi.yaml — regenerated bundles (npm run build:openapi)

Net diff is confined to the cancel path. npm run lint passes.

Requested by @AaryamanBhute

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[akanter]

• docs(transactions): document the 501 response on the cancel endpoint #774 👈 (View in Graphite)
• main

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This PR will update the grid SDKs with the following commit messages.

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chore(internal): regenerate SDK with no functional changes

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kotlin

chore(internal): regenerate SDK with no functional changes

openapi

feat(api): add 501 error response to transactions cancel method

php

chore(internal): regenerate SDK with no functional changes

python

chore(internal): regenerate SDK with no functional changes

ruby

chore(internal): regenerate SDK with no functional changes

typescript

chore(internal): regenerate SDK with no functional changes

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Your SDK build had at least one "note" diagnostic, but this did not represent a regression.
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✅ grid-cli studio · code · diff

Your SDK build had at least one "warning" diagnostic, but this did not represent a regression.
generate ⚠️ → build ❗ → lint ❗ → test ❗

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Last updated: 2026-07-30 19:30:36 UTC

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