perf: drop fabricated timestamp writes from setOptimisticTransactionThread

[adhorodyski]

Explanation of Change

TLDR: On every transaction-row tap, setOptimisticTransactionThread writes lastReadTime / lastVisibleActionCreated with DateUtils.getDBTime() into report_${id}. Because that timestamp is monotonic, the merge ALWAYS produces a diff → report_ collection subscribers fire → 6 derivations recompute (sortedReportActions, outstandingReportsByPolicyID, visibleReportActions, openAndSubmittedReportsByPolicyID, todos, reportAttributes). Measured cost: 156ms–2685ms per tap, sitting before navigation starts → user-perceived press-to-mount jank.

Dropping the two timestamp writes. Structural fields stay; Onyx dedupes them on existing threads → zero cascade.

Why this is safe

Those two lines are armor around an unrelated fix in the same commit (e84c0ad4dbd in PR #72001). That commit narrowed the CREATED-placeholder gate in ReportActionsView.tsx:

- (isMoneyRequestReport(report) || isInvoiceReport(report) || isReportTransactionThread) && !allReportActions?.findLast(isCreatedAction)
+ if (isReportTransactionThread) {
+     return !allReportActions?.findLast(isCreatedAction) && isLoadingInitialReportActions;
+ }

The gate is the real fix. The timestamp writes were redundant defensive armor. Keeping the gate, dropping the armor.

lastReadTime continues to be written post-mount by readNewestAction in ReportActionsList.handleReportChangeMarkAsRead (gated on isUnread() + isVisible + scroll-near-bottom). lastVisibleActionCreated is action-derived — set by action-creating flows (IOU, Task, etc.) with real action timestamps. Neither needs a nav-time fabrication.

Evidence

• Original function in PR #72001 (commit ff567683672, 2025-08-22) wrote only parentReportID + parentReportActionID. No timestamps.
• Timestamps added later in same PR via commit e84c0ad4dbd (2025-09-19, "fix optimistic create report transaction") alongside the ReportActionsView gate change. This PR effectively reverts just the timestamp additions from that commit.
• Related companion: PR perf: split reportMetadata into key groups #88613 (reportMetadata split) exposed the report_ fan-out problem this PR kills at the source.

Measured impact (warm transaction thread re-tap, offline, 5 trials, iOS)

Metric	Pre-fix	Post-fix
6-derivation cascade per tap	156 / 162 / 2685 ms (3 trials)	0 / 0 / 0 / 0 / 0 ms (5 trials)
ManualOpenReport span median	697 ms	574 ms (~−18%)
p95 tail (cascade+span)	~3400 ms	~580 ms

Fixed Issues

$ #88595
PROPOSAL:

Tests

• Verify that no errors appear in the JS console

Offline tests

Covered in QA steps (offline warm-tap is the primary validation path).

QA Steps

1. Existing transaction thread — LHN unread dot:

   • Have a transaction thread with an unread report action (ask another user to comment on it).
   • Observe LHN shows unread dot.
   • Tap the thread row from MoneyRequestReportView.
   • Verify unread dot clears within ~1 frame after ReportActionsList mounts (post-nav), not instantly on press. Matches chat-flow behavior.

2. Arrow navigation in RHP (prev/next):

   • Open a transaction thread in RHP via a multi-transaction expense report.
   • Click prev/next navigation arrows.
   • Verify navigation lands on the correct sibling thread and report header populates correctly. Structural context fields are still written.

3. Optimistic thread creation (new, never-navigated thread):

   • Create a new expense, then tap the transaction row before the server returns (or while offline).
   • Verify the CREATED placeholder renders correctly — must NOT show duplicated, out-of-order, or at wrong position. Thread sorts correctly in LHN.
   • This is the original bug Render optimistic transaction thread #72001 was fixing; ReportActionsView gate (unchanged) should still suppress the issue.

4. Sort ordering in LHN after tap:

   • Note a tapped thread's position in LHN before tap.
   • Tap, navigate in, navigate out.
   • Verify row order didn't shift up unnaturally — previously lastVisibleActionCreated = now could cause artificial reordering.

5. Offline warm-tap, same thread 3× in a row (the perf validation):

   • Go offline.
   • Tap same transaction thread 3 times with 1s between taps (back out each time).
   • Check Sentry ManualOpenReport spans and OnyxDerivedCompute_* spans.
   • Expected: no report_${reportID} merge with hasChanged: true pre-nav; no 6-derivation cascade on taps 2 and 3.

6. Sentry production metric to watch post-merge:

   • OnyxDerivedCompute_outstandingReportsByPolicyID p50/p95 for warm users
   • OnyxDerivedCompute_visibleReportActions p50/p95
   • ManualOpenReport with is_transaction_thread: true — watch for p50 drop

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
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Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari