feat: clarify target labels and fix marker/compass display (#158)

[jrhubott]

Summary

Follow-up on the v2.7.0 #158 work, addressing three trailing items reported during a manual-override divergence:

• Target label clarity (A): the COVERS bar now labels the value "Solar target" (instead of "Target") during an override divergence, with a clarifying marker tooltip. The displayed number is unchanged — it remains the solar would-be position, as shipped in feat: solar target + quieter badge in covers bar (#158) #159.
• Target marker clipping (B): the vertical target marker was clipped/invisible at 100% (and corner-pinned at 0%). It is now centered (translateX(-50%)) and clamped so its full width stays visible at both extremes.
• Sky compass (C): during an override divergence the legend now names both markers — a solid "Cover target" (solar would-be) and a dashed "Cover position (held)" — instead of mislabeling the solid wedge as "Cover position". Both wedges render.

i18n keys added in en + fr; harness scenarios and FALLBACK_LOCALIZATIONS updated to exercise the 100% and 0% target extremes with the compass visible.

Testing

• ✅ 910 tests passing (10 new)
• ✅ tsc strict clean, lint clean, build clean (dist rebuilt)

Related Issues

Refs #158