fix(terminal): defer keyword scroll refresh while Enter is pending

[netcatty-bot]

Summary

• Restore Enter-pending protection so onScroll during the Ubuntu RTT gap (before onWriteParsed) no longer takes the immediate user-scroll keyword path.
• While Enter output is pending, mark the viewport dirty instead of synchronously rescanning; cancel any queued scroll refresh when Enter is pressed.
• When the Enter protection window clears, trigger a debounced write refresh so deferred viewport motion (including user scroll during the window) still catches up.
• Add a regression test for idle Enter + scroll-before-writeParsed after a prior write cleared lastRenderRange.

Why

v1.1.77 claimed to fix keyword highlight flicker on Enter (#2805), but the persistence rewrite dropped the earlier enterInputPending scroll guard. After a normal write refresh, lastRenderRange is null and lastWriteAt goes stale at an idle prompt, so Ubuntu 24.04 echo that emits onScroll before onWriteParsed was again classified as user scroll and synchronously rescanned the viewport — flashing still-visible keyword decorations.

Changes

• components/terminal/keywordHighlight.ts: restore Enter-time scroll deferral + idle-clear catch-up.
• components/terminal/keywordHighlight.test.ts: cover the idle Enter / pre-writeParsed scroll race.

Testing

• node --test --import tsx components/terminal/keywordHighlight.test.ts (47 passed)
• Manual (unverified here): Settings → Terminal → Keyword Highlighting on; SSH to Ubuntu 24.04; press Enter at an idle prompt and confirm existing highlights do not flash.

Fixes #2879

Automation

• Automated implement pass
• Review gate: @codex review (own/bot PRs only)
• Draft until Codex reports clean findings

[binaricat]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 315e596e08

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[chatgpt-codex-connector]

Bound Enter-pending scroll suppression without output

When the remote PTY produces no write after Enter—for example, with echo disabled or a stalled connection—onWriteParsed never runs. enterInputPending is set by onData, but its only clear timer is armed inside onWriteParsed, so this new early return suppresses every subsequent user-scroll refresh indefinitely. Newly revealed scrollback lines therefore remain unscanned and unhighlighted until unrelated output arrives; arm a fallback timer from onData or otherwise time-bound this guard.

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[binaricat]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Another round soon, please!

Reviewed commit: 4935066e53

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

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[netcatty-bot]

Codex reported no major issues. This PR is marked ready for human review/merge.