fix(tui): raise picker selection contrast with inverse + bold

Selected rows in the model/session/skills pickers and approval/clarify
prompts only changed from dim gray to cornsilk, which reads as low
contrast on lighter themes and LCDs (reported during TUI v2 blitz).

Switch the selected row to `inverse bold` with the brand accent color
across modelPicker, sessionPicker, skillsHub, and prompts so the
highlight is terminal-portable and unambiguous. Unselected rows stay
dim. Also extends the sessionPicker middle meta column (which was
always dim) to inherit the row's selection state.

ui-tui/src/__tests__/osc52.test.ts

@@ -49,6 +49,7 @@ describe('readOsc52Clipboard', () => {
       data: `c;${Buffer.from('queried text', 'utf8').toString('base64')}`,
       type: 'osc'
     })
+
     const flush = vi.fn().mockResolvedValue(undefined)
 
     await expect(readOsc52Clipboard({ flush, send })).resolves.toBe('queried text')