fix(PromptComposer): clear empty editor fillers before chip insertion

Insert a helper that strips filler-only editor content (stray <br> and
caret-anchor text nodes) before inserting reference/annotation chips and
on paste, so chips no longer land after an empty line. Also anchor the
caret after each inserted/updated chip and reorder focus/insert so the
caret reliably follows the new chip.

.gitignore

@@ -8,9 +8,4 @@ frontend/.vercel/*
 frontend/.vercel_build_output/*
 output/*
 .DS_Store
-.tools/bin/*
-
-# Embedded external tool/skill repos (checked out locally, not vendored)
-.ai-context/ai-context/
-.ai-context/zero-skills/
-.tools/mcp-zero/
+.tools/bin/*