feat: improve Berdy onboarding tour

[cynfria]

Category: improvement
User Impact: New users get a clearer five-step Berdy tour, and can start chatting with Berdy directly from Home after completing it.
Problem: Berdy's onboarding copy and guided experience no longer reflected the current Home, provider, agent, and skill workflows. The embedded preset-question state also made Berdy behave differently from other agents after onboarding.
Solution: Refresh the localized onboarding flow and artwork, make Berdy use the Home composer like other agents, harden agent repair and drag lifecycle behavior, and keep onboarding experiment controls limited to development builds.

File changes

src/app/AppShell.navigation.test.tsx
Updates navigation coverage for resolving or repairing Berdy before tagging the Home composer.

src/app/AppShell.tsx
Replaces the old prompt-start callback with a safe Berdy persona resolver that repairs the bundled agent when needed.

src/app/ui/AppShellContent.tsx
Threads the focused Berdy resolver into the Home surface.

src/features/design-system/ui/designSystemSections.ts
Moves Input Group to the unused component inventory after removing its last product usage from Berdy's preset-question flow.

src/features/experiments/ExperimentsSettings.tsx
Filters development-only experiment settings from production builds.

src/features/experiments/tests/ExperimentsSettings.test.tsx
Covers production visibility and the development-only onboarding controls.

src/features/experiments/experimentDefinitions.ts
Adds a reusable settings visibility policy and marks onboarding experiments as development-only.

src/features/home/ui/HomeView.tsx
Passes Berdy's agent resolver into the Home widget canvas.

src/features/home/ui/WidgetCanvas.tsx
Forwards Berdy's resolver to rendered widget frames.

src/features/home/ui/WidgetFrame.tsx
Exposes the resolver to the onboarding widget.

src/features/home/widgets/OnboardingTourWidget.test.tsx
Replaces preset-question tests with composer tagging, repair, retry, drag, unmount, and reset lifecycle coverage.

src/features/home/widgets/OnboardingTourWidget.tsx
Simplifies Berdy to the tour welcome state, makes post-tour activation tag the composer, and isolates drag motion from avatar rendering.

src/features/home/widgets/types.ts
Defines the focused Berdy resolution callback across Home widget boundaries.

src/features/onboarding/assets/tour-4-agents.png
Adds the centered agent artwork for tour step four.

src/features/onboarding/ui/OnboardingTourDialog.test.tsx
Updates coverage for the reordered five-step tour and final-step behavior.

src/features/onboarding/ui/OnboardingTourDialog.tsx
Refreshes tour artwork, adds the skills step, reorders provider and chat steps, and removes the final next arrow.

src/shared/i18n/locales/en/home.json
Updates English Berdy welcome and five-step tour copy while removing obsolete preset-question strings.

src/shared/i18n/locales/es/home.json
Updates Spanish Berdy welcome and all five tour steps to match the revised flow.