The composition bar lays segments out against the FULL context window (width
= x / window) while legend/tooltip percentages are shares of the OCCUPIED
part (x / used) — so a slice that is half the used context reads ~20% wide
when the window still has headroom, which looks contradictory.
On hover (segment, legend chip, or the free track) a dashed frame now
outlines the occupied region (left edge to the used/window boundary), making
the 'share of used' reference visible; the frame renders only when a free
track exists (otherwise width already equals the percentage) and is
pointer-events:none. Segment tooltips now append 'of used context'
(zh: 占已用上下文) and legend chips carry the same hint as a title.
Adds the .lc-occupied-box style (shared --dsw-alias tokens), one i18n key per
locale, and render-test assertions that the frame appears on hover and
clears when hover leaves.
bowenliang123
d7b20a2978