#23068 webviews: the Options chip truncates only when its row is full (chip-fixed-width, agent-pane-no-capsules base reds)

Two webview tests have been red on feat-cmux-next since fe0e57b3e1c (pushed directly to base) added the composer's Options chip. This PR fixes both. Neither has the font or metrics cause that compaction-rows is fixing; both are stylesheet rules the tests read.

Test	Base failure	Change
chip-fixed-width	composerControls.css .acpmux-options-text => 180px	Code: the Options chip's face no longer stops at 180px. The chip shrinks with its row (flex: 0 1 auto; min-width: 0, button max-width: 100%) and ellipsizes only when the row is full, as #22731 did for the other chips. In the chat bar a more specific rule wins over the bar's > span { overflow: visible } so the face still ellipsizes.
agent-pane-no-capsules	.acpmux-options .acpmux-picker-button (radius 999px, height 28px)	Test list: the Options chip sits in the same row as the model, effort and access chips, which the test lists as the Claude app's soft pill (#22107). The commit drew it "a quiet pill like the access chip" on purpose, so it joins that list with the reason in the comment. Every other selector is still checked.

Changelog

• Fixed: the composer's Options chip no longer cuts off its label at a fixed width while the row has room.

Observed / Not run

• Base failures: from react-apps-check on #23034 (run 39553495850) and #20393 (run 39554271195), same messages on both.
• scripts/web-lint.sh: clean on these files (the one warning is base's HistoryPage.tsx jsx-a11y). prepush-gate.py: no new violations.
• Not run locally (no tests on this Mac): both files run in this PR's react-apps-check shards.

Agent session: cosmic-gray

🤖 Generated with Claude Code

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Summary by cubic

Fixes two webview tests that went red when the composer's Options chip was added to base.

• The chip's label no longer truncates at a fixed 180px; the chip shrinks with its row and ellipsizes only when the row is full.
• The row counts the chip's whole width first (via a data-fit-natural marker) so label steps occur before the chip gives up any text, and the chip keeps a 56px floor.
• The chip joins the agent-pane-no-capsules pill list alongside the model, effort, and access chips, since it deliberately takes the access chip's shape.