feat(desktop): route first run to provider catalog

[Astro-Han]

Summary

• Render first-run provider recommendations from the registry-owned RECOMMENDED_PROVIDER_TYPES set instead of an onboarding-specific list.
• Add a Browse all providers action that opens the existing Settings provider catalog directly.
• Consume the catalog navigation request after its first loaded model-page mount so normal Settings navigation is preserved.
• Cover the fresh-workspace journey with deterministic fake-backend Playwright E2E coverage.

Why

Phase 6 of #860 requires first-run onboarding to stop owning a parallel provider list and reuse the shared provider catalog established by #863 and #866. This keeps provider recommendation and catalog ownership in the registry while preserving the existing connection-management flow.

Refs #860

Scope

This PR implements Phase 6 only. It does not add providers, change provider configuration behavior, redesign connection management, or implement Phase 7 cleanup and conformance work.

Verification

• npm run typecheck
• npm --workspace @maka/desktop test — 2,399 passed
• npm --workspace @maka/desktop run e2e — 13 passed
• node --test apps/desktop/dist/main/__tests__/icon-governance-contract.test.js — 4 passed
• npm run check:stale — dist is fresh
• Independent reviewer found no P0–P3 findings after the latest main rebase and review-finding fix.

No standalone visual artifact is included. The user-visible change is a navigation action rather than a static appearance change; the deterministic first-run Playwright journey verifies registry-owned recommendation order, direct entry into the shared searchable Settings catalog, and one-shot navigation behavior after returning to model connections.

Brand-asset audit: this PR adds or edits no SVG or provider-brand asset. First-run renders the existing shared ProviderLogo → ProviderBrandMark path. The recommended marks are consumed unchanged from the existing vendor set sourced from lobehub/lobe-icons, npm @lobehub/icons-static-svg@1.91.0, git commit e4302041fbb3039608d25f9f618bd462783b875e, MIT license: icons/siliconcloud.svg, icons/claude-color.svg, icons/openai.svg, icons/gemini-color.svg, icons/moonshot.svg, icons/deepseek-color.svg, and icons/ollama.svg. Plan aliases reuse their provider mark; no plan-specific logo is created.

Impact

Fresh workspaces now show the registry-owned recommended provider set and can open the full provider catalog directly. Existing persisted provider ids, provider configuration, connection management, runtime behavior, credentials, and model selection are unchanged. No migration, documentation update, or release-note entry is required.

Reviewer notes

Review the ownership boundary: onboarding consumes RECOMMENDED_PROVIDER_TYPES, the new action initializes the existing ProvidersPanel catalog, and SettingsSurface consumes that one-shot intent after the first loaded model-page mount. First-run must continue using the shared provider brand-mark path; this PR must not introduce provider SVG assets.

Ready for review

• Verification is complete and the results above are current
• Impact, compatibility, migration, documentation, and release-note needs are addressed
• User-visible UI/UX changes include visual evidence, or Verification explains why it is not applicable