fix(web): measure collapsed model labels at their visible width#9540

Note

Fix providerModelPickerNaturalWidth to measure collapsed model labels at visible width

• providerModelPickerNaturalWidth now treats a label as intentionally collapsed only when both its client width and computed flex growth are zero. Zero-width labels with flexible growth now recover their scroll-width overflow for natural-width calculations.
• Previously every zero-width model label was treated as collapsed, so flexible labels squeezed to zero contributed no width even though their text was still present.
• Adds a test suite covering collapsed labels, flexible truncated labels, flexible zero-width labels, and the existing 180-pixel picker maximum-width cap.
• Risk: labels that are zero-width with non-zero flex growth now contribute recovered text width to picker sizing, which may change layout in narrow composer widths where labels were previously ignored.

^{Macroscope summarized 8309a40.}

Note

Low Risk Localized DOM measurement logic for composer footer layout; behavior change only affects when controls move to overflow at narrow widths.

Overview Fixes resting composer control measurement so narrow layouts no longer reserve space for model label text that is intentionally hidden.

providerModelPickerNaturalWidth now treats a label with zero width and flex-grow: 0 as deliberately collapsed and does not add scrollWidth − clientWidth to the picker’s natural width. Flexible labels (flex-grow not 0) still get truncated text recovered when squeezed, including when clientWidth is 0, and the picker max-width cap is unchanged.

Adds four unit tests for collapsed vs flexible labels, overflow layout at a 200px host, and the max-width ceiling.

^{Reviewed by Cursor Bugbot for commit 8309a40d3aa36566409fcbfba2909a88fc11fe42. Bugbot is set up for automated code reviews on this repo. Configure here.}