Enforce divider range for default splits and drifted dividers

[austinywang]

Addresses the two remaining CodeRabbit findings on #167:

1. Default (nil) divider position bypasses the configured range — normalizedInitialDividerPosition now clamps the implicit 0.5 default into dividerPositionRange instead of passing nil through to the internal hardcoded fallback.
2. Pre-clamped comparison masks out-of-range dividers — syncPosition now compares the raw currentDividerPixels / availableSize ratio, so a divider that physically drifted outside the configured range (non-drag AppKit resize) is re-asserted to the model position instead of early-returning.

Both fixes verified red/green: testDefaultSplitPositionRespectsConfiguredDividerRange fails at 0.5 and testSyncRestoresDividerThatDriftedOutsideConfiguredRange fails at 0.2 without the fixes. Full suite: 184/184 pass.

🤖 Generated with Claude Code

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Summary by cubic

Enforces dividerPositionRange for default split position and restores dividers that drift outside the range after non-drag resizes. Prevents bypassing the configured range and keeps the view in sync with the model.

• Bug Fixes
  • Clamp the implicit 0.5 default into dividerPositionRange in normalizedInitialDividerPosition.
  • In syncPosition, compare the raw ratio (currentDividerPixels / availableSize) and re-assert the clamped model position when the divider drifts out of range.

^{Written for commit 4b46851. Summary will update on new commits.}

Summary by CodeRabbit

• Bug Fixes

  • Divider positions that drift outside the configured range are now automatically restored.
  • Default divider placement now respects configured position limits, including when no initial position is provided.

• Tests

  • Added coverage for restoring out-of-range dividers and clamping default positions to configured limits.

[coderabbitai]

📝 Walkthrough

Walkthrough

Divider initialization now respects configured bounds, while synchronization corrects physical divider drift outside those bounds without changing the stored model position.

Changes

Divider range correction

Layer / File(s)	Summary
Initial divider position normalization Sources/Bonsplit/Public/BonsplitController.swift, Tests/BonsplitTests/EmbeddedConfigurationTests.swift	Initial and default divider positions are clamped to dividerPositionRange, with coverage for a constrained default range.
Out-of-range divider resynchronization Sources/Bonsplit/Internal/Views/SplitContainerView.swift, Tests/BonsplitTests/BonsplitTests.swift	Synchronization compares the un-clamped physical ratio and restores dividers that drift outside the configured range without modifying the stored divider position.

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

Possibly related PRs

• manaflow-ai/bonsplit#132: Also adjusts divider ratio computation and synchronization behavior in SplitContainerView.

🚥 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 two main fixes: clamping default split positions and restoring drifted dividers into range.
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 docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch coderabbit-167-divider-range

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[greptile-apps]

Greptile Summary

This PR keeps split dividers inside the configured range.

• Clamps the implicit default divider position before it reaches the internal split controller.
• Compares the raw divider ratio during split-view sync so drifted dividers are restored.
• Adds tests for default-range clamping and non-drag divider drift.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.
• The sync path still guards zero-size layouts and clamps the final AppKit divider write.
• The default-position change is private and affects only local split creation call sites.

Important Files Changed

Filename	Overview
Sources/Bonsplit/Internal/Views/SplitContainerView.swift	Uses the raw physical divider ratio for sync comparisons while keeping the existing guarded, clamped write path.
Sources/Bonsplit/Public/BonsplitController.swift	Clamps nil split positions to the configured range before calling the internal controller.
Tests/BonsplitTests/BonsplitTests.swift	Adds coverage for restoring a divider that drifted outside the configured range.
Tests/BonsplitTests/EmbeddedConfigurationTests.swift	Adds coverage for default split positions with a narrowed divider range.

_{Reviews (1): Last reviewed commit: "Enforce divider range for default splits..." | Re-trigger Greptile}

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@Sources/Bonsplit/Public/BonsplitController.swift`:
- Around line 601-608: Update the movingTab split path to pass the normalized
divider position into splitPaneWithTab, using
normalizedInitialDividerPosition(_:) before the call, so configured
dividerPositionRange is enforced instead of relying on the internal 0.5 default.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 3d993cd4-ae76-4fcc-bed9-446217a5ad17

📥 Commits

Reviewing files that changed from the base of the PR and between 9a06689 and 4b46851.

📒 Files selected for processing (4)

• Sources/Bonsplit/Internal/Views/SplitContainerView.swift
• Sources/Bonsplit/Public/BonsplitController.swift
• Tests/BonsplitTests/BonsplitTests.swift
• Tests/BonsplitTests/EmbeddedConfigurationTests.swift