fix(editor): preserve decimal number input drafts

[DavidBabinec]

Summary

• preserve in-progress lexical states such as 0. and - while number-backed style fields are focused
• keep the persisted CSSPropertyBag values numeric and finite while retaining live canvas updates
• add regression coverage for decimal opacity entry and negative z-index, plus update the editor references

Root cause

ClassPropertyRow converted every input event to a number immediately. Typing the intermediate value 0. therefore stored 0, and the controlled input rerendered without the decimal point before the next digit could be entered.

Impact

Authors can type decimal values normally into number-backed style controls. Incomplete lexical states never enter the persisted site model, and blur restores the canonical stored value.

Verification

• bun test — 6,218 passed, 1 skipped, 0 failed
• bun run build
• bun run lint
• live Chromium retest: Opacity accepted 0 → 0. → 0.8, retained 0.8 after blur, and restored it after reload

Fixes #230