Let a multi-selection be copied as plain lines as well as a list

Copying several notes only produced a numbered list, which is wrong for
pasting into a prompt that already has structure. The selection now
offers both forms, Shift+click selects a range, and a selection bar
makes it obvious that more than one note is selected. Esc clears the
selection before it hides the panel.

AGENTS.md

@@ -26,12 +26,15 @@ clicking an item copies it back to the clipboard.
   `~/Library/Application Support/Prompt/store.json`; images are PNG files in
   `Images/` next to it, cached in an `NSCache`. Owns all mutations (add,
   toggle done, edit, delete, move, merge, clear done) and clipboard writes
-  (`copy`, `copyAsList`). Saves on every mutation.
+  (`copy`, `copyAsList` for numbered output, `copyAsLines` for plain newlines;
+  both text modes skip image items). Saves on every mutation.
 - `Sources/Prompt/PanelView.swift` — the panel UI. Header (section switcher,
   search, add photos, close), item list, composer. Composer `# Name` creates/
-  switches sections. Click = copy; Cmd+click = multi-select; right-click =
-  context menu (Copy, Copy as List, Done, Edit, Open, Merge, Move To, Delete).
-  Drop target for images/files.
+  switches sections. Click = copy; Cmd+click toggles multi-select, Shift+click
+  selects a range, and a selection bar offers Copy as List / Copy as Lines;
+  right-click = context menu (Copy, Copy as List, Copy as Lines, Done, Edit,
+  Open, Merge, Move To, Delete). Esc clears the selection before it hides the
+  panel. Drop target for images/files.
 - `Sources/Prompt/PanelController.swift` — owns the floating `NSPanel`
   (`.nonactivatingPanel`, `.floating`, right-edge docked, frame autosaved as
   `PromptPanel`), the Cmd+V image-paste monitor, and `EditWindowController`
@@ -156,7 +159,8 @@ brew upgrade --cask prompt
 - **Never bind bare keys as `.keyboardShortcut` in the panel** (Space, Delete,
   plain Cmd+C). SwiftUI key equivalents are matched before text input and
   would steal characters from the composer TextField. Only Cmd-modified
-  shortcuts that TextFields don't use are bound (Cmd+F/K/N, Shift+Cmd+C).
+  shortcuts that TextFields don't use are bound (Cmd+F/K/N, Shift+Cmd+C,
+  Option+Cmd+C).
   This is why Copy has no in-panel shortcut: click-to-copy is the primary
   gesture, matching Copper's intent.
 - The panel is a `.nonactivatingPanel`; its `canBecomeKey` override is what