Fix Caps Word weak shift release (#26086)

[pratyushsinghal7]

Description

Clear Caps Word's weak Left Shift when a normal key is released. This prevents mouse clicks between Caps Word keypresses from acting as Shift-click. Runtime-enabled Auto Shift keeps its existing delayed-key handling.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• Fixes When Caps Word is active, mouse clicks select a range of text #26086

Checklist

• My code follows the code style of this project.
• I have read the PR Checklist document and made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and do not break anything.

Testing

• make test:all
• 82 tests across all six Caps Word configurations
• qmk format-c -n with clang-format 20.1.8
• git diff --check

AI-assisted; reviewed and tested by the contributor.