fix(ticker): respect terminal width during progress updates

[guaguagf]

Problem

The in-place stderr ticker can soft-wrap on narrow terminals or with long run IDs. The next ESC[2K\r clears only one row, leaving ghost output behind.

Root cause

Ticker frames were written without considering process.stderr.columns or terminal display-column width.

Fix

• Read the current stderr terminal width for every frame, so live resizes are respected.
• Clip updates and final lines to columns - 1 and append a one-column ellipsis when truncated.
• Measure terminal display columns for wide glyphs, emoji, combining marks, variation selectors, and controls.
• Truncate only at grapheme-cluster boundaries via Intl.Segmenter, so user-perceived characters are never split.
• Fall back to 80 columns when the width is unavailable or invalid.
• Preserve non-TTY silence and ANSI-free NO_COLOR output.
• Add no runtime dependencies.

Tests

• 27/27 focused ticker tests passed, including truncation, live resize, 80-column fallback, final output, NO_COLOR, CJK width, emoji graphemes, and combining sequences.
• npm test — passed
• npm run test:e2e — 66 passed, 1 skipped
• npm run lint — passed
• npm run typecheck — passed
• npm run format:check — passed
• npm run build — passed

Type of change

• Bug fix (non-breaking change that fixes an issue)

Checklist

• PR targets the main branch.
• Commits follow Conventional Commits.
• Lint, formatting, typecheck, unit tests, and coverage gate pass.
• New behavior is covered by unit tests.
• No secrets, credentials, or personal data are included.

Risk

Low. The change is isolated to ticker rendering, adds no dependencies, and leaves non-TTY behavior unchanged.

Closes #72

Summary by CodeRabbit

Bug Fixes

• Ticker output now fits within the available terminal width.
• Long updates and final lines are truncated at grapheme boundaries with an ellipsis.
• Improved display-width handling for wide characters, emoji, and combining marks.
• Added a fallback for terminals without a reported width.
• Width-limited output now works correctly with or without color formatting.
• Zero-width terminals produce empty ticker output instead of overflowing.

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Reviewing files that changed from the base of the PR and between 5c62296 and 6832e83.

📒 Files selected for processing (1)

• src/lib/ticker.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• src/lib/ticker.ts

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Walkthrough

The ticker clips update and final lines to the current stderr width. It uses an 80-column fallback, re-reads width for each frame, and applies grapheme-aware clipping to ANSI and NO_COLOR output.

Changes

Ticker width handling

Layer / File(s)	Summary
Terminal-width fitting src/lib/ticker.ts	The ticker measures display width for wide characters, emoji, combining marks, variation selectors, and control characters. It truncates at grapheme boundaries, reserves the final column, and appends an ellipsis.
Ticker output integration src/lib/ticker.ts, src/lib/ticker.spec.ts	ANSI and NO_COLOR updates and finalization use the current terminal width. Tests cover resizing, fallback behavior, escape-free output, and Unicode-safe clipping.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 6832e

The PR limits ticker output to the available terminal width while preserving non-TTY behavior, with no actionable merge-blocking risk remaining after normal checks and review.

Possibly related PRs

• TestSprite/testsprite-cli#12: Both changes modify ticker rendering and tests, with this change adding terminal-width clipping to the NO_COLOR path.

Suggested reviewers: zeshi-du

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: making ticker progress updates respect terminal width.
Linked Issues check	✅ Passed	The changes satisfy issue #72 by clipping ticker output, supporting resizing and fallback widths, preserving graphemes, and keeping non-TTY output silent.
Out of Scope Changes check	✅ Passed	The implementation and tests remain focused on terminal-width handling for the progress ticker described in issue #72.

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Actionable comments posted: 1

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Inline comments:
In `@src/lib/ticker.ts`:
- Around line 54-56: Update the ticker truncation logic around the existing
line-length checks to measure terminal display width rather than UTF-16 length,
and truncate only at grapheme-cluster boundaries while preserving the ellipsis
and maxLength edge cases. Add focused tests covering wide glyphs, emoji, and
combining sequences.

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📒 Files selected for processing (2)

• src/lib/ticker.spec.ts
• src/lib/ticker.ts

[guaguagf]

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[zeshi-du]

This sat without a human reply for five days — that's on us, not on the work. Sorry for the silence.

This is a genuinely good fix. Intl.Segmenter for grapheme-cluster boundaries, a real East-Asian-Width table for fullwidth code points, and explicit handling for emoji/ZWJ sequences, variation selectors, and combining marks is more careful than most terminal-width code I see. Re-reading process.stderr.columns on every frame instead of caching it means live resize just works without a SIGWINCH listener, and the 80-column fallback covers the "columns is unavailable" case cleanly. Zero new dependencies for all of that. I also checked that the !tty early return is untouched, so piped/non-TTY/CI output is exactly what it was before this PR.

One thing I'd like changed before merge. fitToTerminal is applied in both branches — the NO_COLOR branch (ticker.ts:179 and :185, writing through stderrWrite) and the ANSI branch (:197 and :203, writing through rawWrite with \x1b[2K\r). But stderrWrite appends a newline: that branch always scrolls, one line per call, and never does the in-place ESC[2K\r rewrite. The ghost-row bug in #72 is specifically a soft-wrap-plus-overwrite problem — it can't happen on a path that never overwrites. So clipping the NO_COLOR branch buys no correctness there and does cost something real: the tail of every long line, for anyone running with NO_COLOR set on a real TTY — a screen reader or a high-contrast terminal setup, for instance, since !tty already makes piped/redirected output completely silent regardless of NO_COLOR. Can you confine the clipping to the in-place (ANSI) branch and leave NO_COLOR output unclipped? The clips NO_COLOR output without adding ANSI sequences spec would need to flip to asserting pass-through instead.

Two smaller things, non-blocking:

• The fullwidth table is a solid approximation but not exhaustive against the full East-Asian-Width spec — fine as-is, just flagging it as a known approximation.
• terminalWidth doesn't discount ANSI sequences embedded inside a caller-supplied line. I checked every current call site and none of them pass colorized text today, so this is latent, not a bug — just something to keep in mind if a future caller ever does.

Separately: fork CI never ran on this PR — the approval gate needed a maintainer click and nobody clicked it for five days. I've approved it now and the runs have completed (head 6832e83). Everything is green except Dependency Review, which fails on every PR in this repo right now because our org-level dependency graph is disabled — that's on our infrastructure, not this diff. Ignore it.

One more thing worth knowing for next time: that approval gate re-arms on every new push from a first-time contributor, and the nudge bot that pings on CI failure only fires on a completed run — a run that never starts produces no notification at all, so your checks tab would just look empty with no explanation. If a future push here (or on #310) sits with no checks running, ping rather than assume something's wrong on your end.