Theme colors in place of the dark-mode patches; labels as chips

[mattshax]

Theme colors in place of the dark-mode patches; labels as chips

After the shared theme (v1.91), 67 [data-theme='dark'] rules were still patching colors that light-mode rules hard-coded. Some of them had begun to work against the theme: the dark multi-select colors overrode the new warning tints, and the dark shadows were literal blacks. Headings, paths, and labels were also drawn in navy, a color neither the platform nor the other apps use for static text.

What changed

• Each light-mode rule that hard-coded a color now uses the theme token that applies in both schemes, and its dark patch is deleted. This removes 51 dark rules and 89 color literals.
• Headings and titles use the text color: view titles, chart and list headings, task and fleet headings, the brand name, and empty-state titles. Empty-state titles are now 14px / 500.
• Paths: search results, Stats rows, and query cells use the text color and turn the link color on hover. The viewer's path uses the muted color.
• Tree rows: folders and files use the text color, and chevrons the muted color.
• Selections, notices, and banners:
  • multi-select rows and bars, the index notice, and the approvals box use --theme-warning-muted, with warning text mixed toward the text color;
  • the external-endpoint banners use the success and error tints;
  • destructive menu items use --theme-error.
• Search-mode pills: full text uses the theme's info tint, by meaning uses violet tinted from the theme, and name uses neutral.
• Labels become a bordered chip with a 6px dot. An applied label has a success tint and dot, and an inherited one a dashed border and a muted dot. Tree tags are bordered and muted.
• Bars and shadows: chart bars use the accent, and menus, panels, and banners use --theme-shadow-lg, which the theme sets per scheme.
• Code and text bodies use --theme-muted-panel-bg.
• Links use --theme-link site-wide. Conversation rows in the chat rail keep the text color in both schemes.

Kept on purpose (16 rules):

• the derived theme defaults;
• the workflow diagram's text;
• the find highlights;
• the 3D canvas gradient;
• code blocks;
• the accent swatches in Settings;
• the tool spec box;
• the chat rail's selected row;
• the package's toggle switch.

Checked.

• Screenshots in light and dark of Search with results, Library, Stats, and Chat.
• Server tests (237) and web tests (66) pass.