fix: resolve off-by-one in ModeWidget._clear() keeping tonic active

[rakshaak29]

Description

This PR resolves a critical off-by-one bug in the Mode Widget where the _clear() method failed to deselect the root/tonic note (index 0).
Because _selectedNotes[0] was never cleared, a cascade of silent failures occurred whenever a user attempted to clear the widget to build a new mode from scratch:

• Data Corruption: The _calculateMode() logic would evaluate the single note as [12], which _save() would blindly overwrite into localStorage.custommode, clobbering the user's legitimately saved custom modes.
• Mislabeled Export: Since [12] does not match any valid entry in MUSICALMODES, _setModeName() would blank the mode label, causing the generated action and definemode blocks to always incorrectly default to the name "custom".
• Broken Features: The Rotate animations (_rotateRight / _rotateLeft) immediately abort if _selectedNotes[0] is true, meaning rotation was permanently broken after clicking Clear.
• UI/UX: The wheel retained a "ghost" selection, confusing users.

PR Category

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

Changes Made

• js/widgets/modewidget.js: Updated the loop bounds in _clear() to initialize at i = 0 instead of i = 1, ensuring all 12 note positions are properly deselected.
• js/widgets/__tests__/modewidget.test.js: Updated the should clear all notes except root test. The test was originally written to explicitly expect this broken behavior. It has been renamed to should clear all notes including root and updated to assert that _selectedNotes[0] evaluates to false.

Testing Performed

• Unit Tests: Ran npm test. All 5,006 tests across 152 suites pass successfully.
• Manual Verification: Verified that clicking the Clear button now fully clears the wheel, rotation animations function normally, and custom modes can be saved without data corruption.

[github-actions]

🧪 Jest Test Results

❌ Some Jest tests failed. Please check the logs and fix the issues before merging.

Coverage: Statements: 45.18% | Branches: 36.53% | Functions: 50.56% | Lines: 45.62%

Note: These failures may be introduced by this PR or may already exist in the master branch.
Tip: Update your branch with the latest master and rerun tests.
If the same failures are present on master, they are likely not introduced by this PR.

Failed Tests:

planetInterface.test.js

[github-actions]

This pull request has been open for more than 60 days without any activity. It will be closed in 3 days unless the stale label is removed or commented on.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.27%. Comparing base (e58db21) to head (1c78c3b).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7218   +/-   ##
=======================================
  Coverage   59.27%   59.27%           
=======================================
  Files         176      176           
  Lines       57975    57975           
=======================================
  Hits        34365    34365           
  Misses      23610    23610           

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