[everpcpc]

Problem

The bubble shape preference added in #1286 did not work out in practice:

• With whole-bubble (YOLO) boxes, the rounded-rectangle text area spanned nearly the full box, so translations looked oversized; the ellipse shrank the text area to 0.5 of the box, making the same text too small.
• The white blob was the detected box plus an outward feather band, so it painted over the bubble's own border line and left a blurry halo outside the bubble.
• Horizontal font fitting was capped (4 iterations, at most ×0.7 per step), so longer translations failed to converge, overflowed the text area, and pressed against the bubble edge.

Fix

• Drop the shape preference entirely; bubbles always render as rounded rectangles. The stale bubbleShape key in stored preferences is ignored on decode, and its three localization keys (Bubble Shape / Ellipse / Rounded Rectangle) are removed.
• Whole-bubble boxes now keep the blob and its feather inside the detected box, so the bubble's own border line survives instead of being covered and blurred; text-tight (rt_detr) boxes keep the outward feather since the blob must grow past the glyphs.
• The whole-bubble text area is a centered 0.5 of the box, keeping glyphs off the bubble's own padding.
• Horizontal fitFont converges like the vertical path (×0.85 steps down to the 8pt floor) instead of giving up and overflowing.

Validation

• make format, make build: iOS / macOS / tvOS all pass.
• make localize run; ./misc/translate.py list reports no missing translations.
• Manual verification on simulator pages detected by the YOLO model: bubble borders stay visible, no halo outside the bubble, translated text (horizontal and vertical) stays inside the bubble.