fix: bind converted KiCad reference text to the instance name

[billythompsons]

Fixes #4708.

Problem

tsci convert copies the KiCad fp_text reference placeholder into a literal text="REF**", so every placed instance of the converted footprint prints "REF**" instead of its reference designator.

Fix

After convertCircuitJsonToTscircuit runs, the KiCad reference placeholder (text="REF**" on a silkscreentext) is rebound to the component instance: text={props.name ?? "REF**"}. Ordinary user text stays literal, and the rewrite only applies when the generated component has props in scope.

Kept this in the CLI's convert path since the placeholder is a KiCad artifact known at conversion time; happy to move it into circuit-json-to-tscircuit if you'd rather handle it there.

Tests

• convert-kicad-mod-reference-text.test.ts: converts the issue's two-pad .kicad_mod plus an fp_text user control - asserts the reference placeholder is rebound and user text stays literal.
• convert-kicad-mod-reference-e2e.test.ts: builds a board with two instances (U1, U2) and asserts the emitted pcb_silkscreen_text values are exactly ["U1", "U2"] (the issue's failing scenario).

Full tests/cli/convert suite passes.