feat(results): visual row selection and batch DELETE query generation

[pixelEDI]

Summary

• Add visual row selection in Results (v, expand with j/k, exit with v/Esc)
• Generate batch DELETE for selected rows via D
• For single-PK tables, generate compact IN (...) clause and dedupe ids
• Replace unrelated existing query text (e.g. previous SELECT) when generating
  DELETE

Why

Deleting multiple rows from results previously required single-row iteration and
manual query cleanup. This adds a fast, safe workflow for multi-row delete query
generation.

UX / Keybindings

• v is intentionally used for selection because this is Vim-native behavior
  (visual selection), which fits existing sqlit keybinding conventions.

Notes

• Keeps existing behavior for non-single-PK/mixed cases by falling back to OR
  predicates
• Query generation still happens in editor first (user executes manually)

Testing

• Manually tested in sqlit@dev:
  • visual selection highlighting
  • multi-row D delete generation
  • dedupe/merge behavior
  • replacing previous non-DELETE query text