fix: 'zoom to timeline' now scales the timeline to 95% of the viewport

[PlkMarudny]

What does this PR do?

'Zoom to timeline' ( shortcut Z) feature now scales the timeline so that it it fits within 95% of the available space.

Type of change

• Bug fix
• New feature (transition / preset / text anim / effect / API)
• Docs
• Refactor / internal

How was it verified?

• node --check server.js && node --check app.js && node --check mcp-server.js passes
• Opened the editor and confirmed the change in preview
• Confirmed the change in an export (fast or realtime), if it affects rendering
• Updated CLAUDE.md / README.md if the schema, props, or API changed

Checklist

• No new runtime dependencies added
• Preview and export render identically (single compositor)
• Commits are focused and messages are descriptive

Summary by CodeRabbit

• Bug Fixes
  • Timeline zoom-to-fit now fills approximately 95% of the visible timeline width for a more consistent view.
  • Removed unnecessary trailing space from zoom-to-fit calculations.
  • Timeline duration no longer expands incorrectly when clips reference unavailable tracks.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: c27fe263-a3d3-4998-b11a-92bde01b128a

📥 Commits

Reviewing files that changed from the base of the PR and between 6ec153e and 4664b70.

📒 Files selected for processing (1)

• app.js

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📝 Walkthrough

Walkthrough

Changes

Timeline fit behavior

Layer / File(s)	Summary
Valid clip duration calculation app.js	projDur() ignores clips referencing unknown tracks and excludes non-finite clip end times when calculating the timeline duration.
Viewport-based zoom fitting app.js	zoomToFit() uses the project duration without trailing padding, scales content to 95% of the viewport, and scrolls to the timeline start.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: xusnitdinov

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 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 primary change to Zoom to timeline behavior and the 95% viewport fit.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[ronak-create]

Approving — small, correct, and the comments explain the reasoning.

Two notes for the record rather than changes:

• Dropping TIMELINE_PAD_SEC from the fit span is the right call, but since contentWidth() still adds it, a horizontal scrollbar will now always be present after a Fit. That matches how Fit behaves in other NLEs, so I read it as intended — just flagging it since the old comment explicitly promised "no horizontal overflow".
• The projDur() hardening (skipping clips whose track is not in TRACKS, guarding non-finite ends) goes a little beyond the title. It is a safe improvement — projDur() also feeds the export duration, and a clip on a nonexistent track is not rendered anyway — so no objection, it just deserves a mention in the description.

Conflicts with none of the other open PRs, so this one goes in first.