fix(timer): prevent division by zero in progress calculation and sanitize negative settings input

[hoanghaoz]

Summary by CodeRabbit

Bug Fixes

• Improved robustness of progress calculation to prevent invalid values in edge cases
• Enhanced timer duration settings validation to prevent invalid configurations and automatically enforce a 1-minute minimum

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 86c0aaf7-4e08-40eb-85c2-e6d4b5c70c95

📥 Commits

Reviewing files that changed from the base of the PR and between 2bdbda5 and 1b8984e.

📒 Files selected for processing (1)

• src/lib/features/note/viewmodel/focus_viewmodel.dart

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📝 Walkthrough

Walkthrough

Updated the focus viewmodel to add defensive validation: the progress getter now guards against division by zero, returning 0.0 for invalid totalTime values and clamping results to [0.0, 1.0], while updateSettings(...) validates and coerces non-positive duration parameters to safe defaults.

Changes

Cohort / File(s)	Summary
Input Validation & Guard Clauses src/lib/features/note/viewmodel/focus_viewmodel.dart	Added zero-check guard to progress getter to prevent invalid calculations; introduced input validation in updateSettings(...) to coerce non-positive Pomodoro/break minutes to minimum safe value of 1 with error logging.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 Hop hop, the timers now stand tall,
No division by zero shall make us fall,
With guards in place and bounds held tight,
The Pomodoro dream burns ever bright! ⏲️✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the two main bug fixes: preventing division by zero in progress calculation and sanitizing negative settings input.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/countdown_timer

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