refactor(db): one check for a refused conditional write

[alukach]

Seven places checked by hand whether a DynamoDB write was refused by its ConditionExpression, in three spellings (error instanceof Error && error.name === …, (error as { name?: string })?.name === …, and a local isConcurrentEdit). They now call isConditionalCheckFailed from src/lib/clients/database/errors.ts:

• clients/database: accounts.ts, account-trusts.ts, data-connections.ts, products.ts
• actions: account.ts, service-accounts.ts, product-mirrors.ts (isConcurrentEdit stays as a name for what the failure means there)

The helper matches by name, as every copy did, so it also holds for the plain errors tests throw. It's in its own module rather than re-exported from @/lib/clients, because several action tests mock that module with a factory and would otherwise get undefined.

actions/data-connections.ts still has its own two copies. #657 rewrites that file and replaces them with one in operations/data-connections.ts, which will switch to this helper once this merges. Leaving the file alone here keeps the two PRs from conflicting.

Docs and ADRs

No behavior change, so no docs, ADR or llms.txt line is affected.

Testing

• npm run type-check passes.
• The full jest suite passes: 87 suites, 899 tests. The existing tests for duplicate accounts, service-account ids, data-connection upserts and concurrent mirror edits throw ConditionalCheckFailedException-named errors through these paths.

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[claude]

Claude finished @alukach's task in 16s —— View job

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✅ No blocking issues — safe to merge.

(The PR is already merged.) I read the final state of the call sites. isConditionalCheckFailed in src/lib/clients/database/errors.ts matches by name and tolerates null and undefined. It is equivalent to all three spellings it replaced, so there is no behavior change. Keeping it out of the @/lib/clients barrel is sound, given the factory mocks.

Docs

No docs, ADR or llms.txt page is affected. The PR description says so explicitly, which meets the CLAUDE.md requirement.

Simplify (ponytail)

• src/lib/actions/product-mirrors.ts: the local isConcurrentEdit alias is now a thin wrapper, if it still exists as a function. Inline isConditionalCheckFailed at the call sites, or keep the alias only if the name carries real meaning. Four call sites already use the helper directly.
• src/lib/actions/data-connections.ts:161,286: two hand-rolled copies remain. The PR description says feat(api): data connections, including account-owned ones #657 will fold them in, so no action is needed here.

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💰 Estimated review cost: $0.12 · 0m15s · 6 turns