Orchestrator tab: choose the colour of its outline and divider #245

Owner, 2026-10-16: "I want to be able to choose the color later."

The orchestrator tab (PR #244, Settings > Agents > Orchestrator) is marked by an outline and a divider in the accent colour. Add a colour choice for that mark, like the agent mark colours (one colour picker with alpha, #112; the theme's accent when unset), and keep the contrast floor (the owner works zoomed in and needs the mark to read clearly).

Where: src/renderer/src/components/TabStrip.tsx and TabSidebar.tsx (the lead outline and data-tab-lead-divider rule), a row in the Orchestrator section of the Agents page.

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