perf: scope reportAttributes error propagation to changed chats

[adhorodyski]

Explanation of Change

The reportAttributes Onyx derived value recomputes on every change to any of its 14 dependency keys (every chat message, transaction, or violation tick). Its per-report pass is incremental, but the "propagate errors from IOU reports to parent chats" pass that runs after it walked all reports on every compute (building two full maps) and re-stamped every errored chat each pass. On large accounts (30-50k reports) this is a constant O(all reports) tax per tick — the hottest remaining full scan after PRs #95944 and #95931.

Fix: a module-level chat→children index (childToChat / childrenByChat) is rebuilt on full recomputes and patched incrementally from sourceValues report deltas — the same pattern already used by the sibling derived value reportTransactionsAndViolations.ts (PR #65247). The propagation pass now only re-checks chats present in dataToIterate instead of every report in the account.

Safety invariant: every code path that enqueues a child report for recompute must also enqueue its parent chat. This already held for report/transaction/violation updates; the parent-chat enqueue was moved to run after all update branches so it also covers the policy-tags path. A child that is deleted or moves to another chat now re-enqueues the chat it left, so that chat's propagated error is re-evaluated instead of going stale.

Net effect: full recomputes behave exactly as before (dataToIterate = all reports); single-report/incremental updates on large accounts no longer pay the full-account scan.

Fixed Issues

$
PROPOSAL:

Tests

1. On a workspace with an expense report carrying an error/violation, verify the workspace chat shows the RBR/Fix badge.
2. Clear the error on that expense and verify the chat's error indicator clears.
3. Delete the errored expense offline and verify the chat's error indicator clears once the delete syncs.
4. tests/unit/reportAttributesTest.ts: 27/27 passing (21 existing + 6 new covering: parent flagged by errored child; parent stays flagged while a sibling is errored; parent unflagged when all children clear; flag moves when a child moves chats; flag cleared when an errored child is deleted; unrelated errored chat entries carried by reference on single-report updates). 3 of the new tests fail against main's implementation — they document the behavior change (stale-dot fix) this PR makes.
5. Verified locally: full jest suite green, eslint 0 errors (seatbelt budget unchanged at 24 — new tests written cast-free), typecheck-tsgo clean for the changed files.

• Verify that no errors appear in the JS console

Offline tests

Same unit suite as above — the propagation logic is offline-first client code that runs entirely from local Onyx state, with no network dependency.

QA Steps

Same as tests.

// TODO: These must be filled out, or the issue title must include "[No QA]."

• Verify that no errors appear in the JS console

PR Author Checklist

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Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari