Add copy column data feature with multi-selector dialog

[clobrano]

Summary

This PR adds a new "copy column data" feature that allows users to select and copy individual or combined column values from table rows to the clipboard.

Key Changes

• New MultiSelectorModel component (internal/tui/components/dialog/multiselector.go): A reusable floating dialog that allows toggling multiple items with spacebar and confirming selection with enter. Supports keyboard navigation (j/k or arrow keys) and displays checkboxes for selected items.

• Copy data dialog integration (internal/tui/app.go):

  • Added ViewCopy state to handle the copy dialog overlay
  • Implemented openCopySelector() to build column options from the current table row
  • Added special "NAME+NS" combined option that formats as <name> --namespace <namespace> for convenience
  • Implemented copyToClipboard() command that tries multiple clipboard tools (xclip, xsel, pbcopy) for cross-platform support

• Keybinding updates (internal/tui/keys.go, internal/config/config.go, internal/config/defaults.go):

  • Added new CopyData keybinding (default: c)
  • Changed SwitchContext keybinding from c to C to avoid conflict
  • Updated help text to display the new copy command

Implementation Details

• The multi-selector dialog displays column headers with their values in a compact format (%-12s %s)
• Supports scrolling through items when there are more than 10 visible items
• If no items are explicitly selected, pressing enter selects the currently highlighted item
• Clipboard operations are non-blocking and gracefully fail if no clipboard tool is available
• The dialog is rendered as a full-screen overlay centered on the terminal

https://claude.ai/code/session_01XXnSRgHebTqJjoinv3Yz7k