Refactor text-object behavior and add count support for vil

[kibi2]

This PR includes several small improvements and refactoring around text-objects and block handling.

Changes

• Add count support to "vil" (e.g. v3il)
• Rename motions:
  • motion.g / motion.G
  • → motion.block_top / motion.block_bottom
• Treat the entire file as a block when no plain block exists

Notes

• This makes text-object behavior more consistent and predictable
• Improves internal naming clarity for future extensions
• Prepares for further structural improvements (e.g. upcoming parser / GFM work)

No breaking changes intended, but internal behavior around block detection has been slightly adjusted.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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