fix: use i32 for use_component_rect to prevent overflow

[domenkozar]

Summary

• canvas_position() returns Point<i16> and size() returns Size<u16>. Combining them in a Rect<u16> caused arithmetic overflow for off-screen components inside a ScrollView.
• Changed use_component_rect to use i32 to prevent the overflow.

Test plan

• Verified that components inside a ScrollView that are off-screen no longer cause arithmetic overflow panics.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.06%. Comparing base (766e650) to head (99ed0b9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #176   +/-   ##
=======================================
  Coverage   89.06%   89.06%           
=======================================
  Files          34       34           
  Lines        5826     5826           
  Branches     5826     5826           
=======================================
  Hits         5189     5189           
  Misses        526      526           
  Partials      111      111           

Files with missing lines	Coverage Δ
packages/iocraft/src/hooks/use_component_rect.rs	97.56% <100.00%> (ø)

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[ccbrown]

Looks fine to me, especially since this is still unreleased.

I've been considering a breaking change to replace all of the 16 bit types with 32 bit types anyway since there may be reasonable cases where coordinates beyond 65,535 are possible.

[domenkozar]

Yeah I was looking at making size() return i16 and gave up as it may be too much breakage :) I do appreciate a clean api so 👍 from me