🤖 feat: expand mobile run settings sheet

- Replace ModelPickerSheet with multi-section RunSettingsSheet
- Add mode, reasoning, and 1M context controls alongside model search
- Wire WorkspaceScreen to set modes/thinking/context directly from sheet

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Change-Id: I5fe86aa251a08fe5d3201860af01f74e60e6d926
Signed-off-by: Test <test@example.com>

Author: Test