fix(pi-fff): keep collapsed result row within available width

[Ray0907]

Problem

CollapsedText.render (packages/pi-fff/src/index.ts) can return a row wider than the width it was given. When the first-line preview does not fit, it slices the preview to max(0, previewWidth - markerWidth) columns but still appends the full 3-column ... marker, so the row is markerWidth + 1 + suffixWidth columns even when previewWidth < markerWidth.

I hit this while using the pi coding agent with pi-fff installed (agent was mid-task). pi-tui requires every rendered line to be <= width; otherwise the TUI stops and throws Rendered line N exceeds terminal width, so the whole agent exits and the in-flight work is lost. Seen with @ff-labs/pi-fff 0.11.0 on @earendil-works/pi-coding-agent 0.99.2, in a 24-column pane, after an ffgrep call returned 218 lines:

Terminal width: 24
Line 1012 visible width: 25
[1011] (w=24)  ffgrep /REF|existsS...
[1012] (w=25)  ... ... (217 more lines)

The tool box is Box(1,1), so the component gets 22 columns; the suffix ... (217 more lines) is 20, leaving previewWidth = 1; the output was ... ... (217 more lines) (24 columns) plus 1 left pad = 25.

Fix

If previewWidth < markerWidth, return only the suffix. The Math.max(0, ...) clamp is no longer needed.

if (previewWidth < markerWidth) return [this.suffix];

Verification

• bun test test/: 96 pass.
• Swept widths 1-120 x several line counts x short, long, ANSI-coloured, CJK and empty previews through the real pi-tui Box(1,1), visibleWidth and sliceByColumn: 104 of 7800 combinations overflowed before, 0 after. Wider layouts produce the same output as before.
• Not tested end to end in a running pi with a model.

Side effect: at very narrow widths the collapsed row drops the leading ... and shows only ... (N more lines).

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ℹ️ Recent review info

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Reviewing files that changed from the base of the PR and between 89c1927 and 23740b4.

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• packages/pi-fff/src/index.ts

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📝 Walkthrough

Walkthrough

CollapsedText.render now returns only the suffix when the available preview width is narrower than the marker. Otherwise, it slices the preview using the available width.

Changes

Collapsed text rendering

Layer / File(s)	Summary
Preview width handling packages/pi-fff/src/index.ts	When the preview width is less than the marker width, rendering returns only the suffix. Otherwise, preview slicing uses the available width without a clamp.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~5 minutes

Change: Bug fix

Suggested reviewers: gustav-fff

Merge Risk: ⚪ Minimal · up to 23740

The narrow preview change preserves the rendered-line width limit. No identified issue prevents merging.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the fix and its purpose: keeping the collapsed result row within the available width.

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