feat(design-requirements): always show Winding 1 with a locked ratio and editable label

[gpitel]

What

Single-winding (inductor) designs previously showed no winding row in Design Requirements → Turns Ratios — the section was hidden whenever there were zero ratios, so Winding 1's label could not be seen or edited.

This adds Winding 1 as a reference row: its turns ratio is fixed at 1 and is not editable, but its label is editable (persists to coil.functionalDescription[0].name). The section now renders even for a single winding. Transformers are unchanged — Winding 1 simply appears above the editable ratio rows for windings 2..N.

Implementation

• ArrayDimensionWithTolerance.vue — opt-in referenceWinding prop renders the leading locked-ratio + editable-label row. The shared component is otherwise untouched, so the leakage-inductance / stray-capacitance usages are unaffected.
• DesignRequirements.vue — show the turns-ratio block whenever turnsRatios != null (not only when length > 0), and pass :referenceWinding="true" to that instance only.
• Also folds in the related winding-label work: new windings default to Winding N, and each ratio row is titled by the winding name.

Verification

Verified live on the dev stack with Playwright:

• Inductor (1 winding): the Winding 1 row appears, the ratio is a locked 1 (a non-editable span), and editing the label persisted to the winding name.
• Transformer (2 windings): the Winding 1 reference row plus exactly one editable ratio row (Winding 2).

🤖 Generated with Claude Code