fix(ui): coherent no-crop scaling for pinned layout widgets

Pinned row widgets scaled by container width against hard-coded natural
sizes, so wide-short frames blew text past the frame (Log/Exp row),
wrong guesses cropped content (Trail box), and value boxes stretched to
the container while their text stayed tiny (Samples / Spike MAD).

Adopt the ASTH row model everywhere: height drives text scale, width
surplus feeds the row's single flexible element (pin_flex_width), and
width caps the scale so content never crops. Natural sizes are now
measured per pin and cached (scale-normalized, flex at minimum) instead
of guessed. The layout resize handle enforces the same envelope
(clamp_pin_frame_to_content) and shrinks 18px -> 14px; ASTH rows get
width caps via analytic minimum widths and seed the same envelope.

Rules documented in memory/pinned_widget_scaling.md (local memory dir).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: x-iso