Preserve TUI picker selection after detail views

## Problem

`PaginatedTablePicker` keeps its cursor only in component-local state. Opening a selected resource unmounts the picker, so returning from its detail screen resets the cursor to the first row. This affects every resource flow built on the shared picker.

## Expected experience

- preserve the selected row by stable value when a picker opens a detail screen
- restore that row when the user returns with Escape
- apply the behavior once in `PaginatedTablePicker` for every resource family
- keep existing pagination, resize, transition, and filtering reset behavior
- avoid resource-specific cursor state in individual screens

## Verification

- shared Harness picker regression
- Memory Event picker regression
- full repository coverage suite
- TUI-harness validation across both resource families

Start by locating the shared PaginatedTablePicker and trace how opening a resource detail view unmounts it and how Escape returns to the picker. Run the shared Harness picker and Memory Event picker regressions first; done means the selected row is restored by stable value while pagination, resize, transitions, and filtering resets remain unchanged, with the full coverage and TUI-harness suites passing.

Written by the indexing model from the issue text.