feat(app): surface recent models in picker (#19935)

[dzianisv]

Summary

• surface recently used models at the top of the app model picker under a dedicated Recent section
• preserve recency order for recent models while keeping the existing provider grouping for the rest of the list
• add an e2e check that verifies the seeded recent model appears first in the picker

Testing

• bun typecheck
• bun test:e2e:local -- -- e2e/models/model-picker.spec.ts

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