fix(replay): make inspector navigation responsive

[lordspline]

Problem

Session replay users can lose inspector destinations and controls when a resized sidebar becomes narrower than their labels.

The top-level tabs and inspector rails overflow independently, so hidden actions lack a clear pointer or keyboard affordance.

Refs PostHog#35366

Changes

• Switches top-level tabs to a labeled menu when the sidebar container is constrained.
• Keeps all six available destinations visible as tabs when the sidebar is wide enough.
• Adds explicit scroll controls to narrow filter and settings rails.
• Adds roving keyboard selection and selected-tab auto-scroll to LemonTabs.

Before at 320 px	After at 320 px

All six conditional destinations remain visible at a wide sidebar:

Open video

How did you test this code?

• Added LemonTabs regressions for keyboard selection and selected-tab scrolling.
• Ran the LemonTabs and player sidebar logic Jest suites.
• Ran the frontend TypeScript check and hogli ci:preflight --fix.
• Used Playwright against Storybook at 1280×720, 1440×900, and 1512×982.
• Verified 320 px and 820 px sidebars with all conditional tabs, pointer input, keyboard input, and a longer localized label.
• The full-player story still emits unrelated 404s for missing Replay vision and shell mocks.

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

Automatic notifications

• Publish to changelog?

Docs update

None. This changes the layout of existing navigation without changing a documented workflow.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Capy authored the change and used Storybook plus Playwright for visual verification. It invoked /writing-ui-components, /writing-tests, /writing-user-facing-copy, /writing-code-comments, /qa-frontend, and /writing-pr-descriptions.

The experiment compared scroll-only, wrapped, and adaptive-menu concepts. The committed fixtures use existing repository mocks plus invented example.com issue data.

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