[FEATURE] Bedrock: per-user cost tracking metadata in usage JSONL (follow-up #32104)

Follow-up to #32104

That issue was auto-closed as stale; reopening wasn’t available from my account, so opening this to keep the request visible.

Problem (unchanged)

Teams using Claude Code on AWS Bedrock with a shared AWS account still can’t break down costs per developer in Cost Explorer because invocations don’t carry user-identifying metadata, and Bedrock doesn’t support per-request cost allocation tags.

Ask (same as #32104)

Include identifiable fields in local usage JSONL (e.g. OS username or configurable id, optional awsAccount / provider when on Bedrock), or a claude usage-style summary, so teams can aggregate per user from logs.

Prior discussion

Full context, references, and prior labels: #32104

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If maintainers prefer a single thread, please reopen #32104 and close this as duplicate.