[P3] Text primitive

[fissible]

Centralize all text rendering rules. This becomes the base for labels, titles, status lines, table cells, and menu items.

Needs:

• plain text rendering to coordinates
• width clipping (ANSI-aware)
• truncation with ellipsis
• optional word wrapping
• alignment: left / center / right
• style support (bold, dim, color via ANSI)

Deliverable: src/text.sh with shellframe_text_render.
Effort: M (~half day) | Phase: 3 | Deps: P2 clipping helpers