feat(editor): add inspector picker components

[joaopcm]

Summary

• Add 6 picker/layout components: NumberInput, PaddingPicker, BorderPicker, BorderRadiusPicker, PropRow, Section (with initialCollapsed)
• Add 12 new SVG icons for directional controls (corner markers, panel sides, plus, x, square variants)
• Add CSS layout rules for prop-row and section components
• All components adapted to use our simple HTML primitives (not Radix-style APIs from the old approach)

Context

Part of the inspector sidebar redesign (PRODUCT-1739). These composed components sit between the UI primitives (PR #3185) and the upcoming section components (Inspector.Background, Inspector.Padding, etc.).

Skipped PropertyGroups and StylePanel from the old PR #3173 — those were tied to the JSON-config approach we're replacing.

Depends on #3183 (hooks) and #3185 (primitives).

Test plan

• pnpm lint:fix passes
• All 119 existing inspector tests still pass
• All 12 new icons used by the picker components

---

Summary by cubic

Add reusable inspector picker components (border, padding, border radius, number) and lightweight layout wrappers to standardize the inspector UI on HTML primitives. This advances the inspector sidebar redesign (PRODUCT-1739).

• New Features
  • BorderPicker, PaddingPicker, BorderRadiusPicker: uniform/per-side modes, drag-to-change, and shorthand handling; px/% where applicable.
  • NumberInput: numeric field with unit display/select and drag-to-change.
  • Section (collapsible with optional add/remove) and PropRow for consistent rows.
  • 12 new SVG icons (corners, panels, square variants, plus, x) exported via icons/index.ts.
  • New CSS rules for prop rows and sections; all components use our HTML primitives (not Radix-style APIs).

^{Written for commit 07e5e07. Summary will update on new commits.}

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Project	Deployment	Actions	Updated (UTC)
react-email	Ready	Preview, Comment	Apr 6, 2026 6:23pm
react-email-demo	Ready	Preview, Comment	Apr 6, 2026 6:23pm
react-email-examples	Ready	Preview, Comment	Apr 6, 2026 6:23pm

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Latest commit: 07e5e07

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commit: 07e5e07