pi-image-paths: attach dropped image paths and draw them in the chat

A screenshot is normally sent to pi as a path, so the model gets its text and
the reader gets nothing: pi renders image blocks in tool results but never on
user messages. This extension closes both halves — the path collapses to
"[Image #N]" as you type or on send, and the picture is drawn below the sent
message.

The rewrite is a terminal-input listener that re-reads a settled editor, joins
word by word for paths with unescaped spaces, and reports a path that does not
exist instead of eating the prompt. The drawing appends a custom session entry
carrying the message's image blocks, one macrotask after message_end so it lands
below the message pi persists afterwards, and renders it with pi-tui's inline
image component under terminal.showImages and terminal.imageWidthCells. Entries
stay out of the model context, so each image is still sent to the model once.

Tests: npm test (21, node:test over a stand-in for pi: rewrite, send-time
attachment, missing paths, append gate, renderer gating) and npm run typecheck.

Co-Authored-By: nw-flash-flex <noreply@freno.me>

.gitignore

@@ -0,0 +1,7 @@
+.DS_Store
+node_modules/
+dist/
+.pi-lens/
+.ralpi/
+package-lock.json
+.worktrees/