Folds the standalone ThreeTxtFileHelper tool into URLNotesGrabberCORE so
text-file ingest/output/correct lives alongside the API scraper. Adds
new flags -ingest, -output, -correct (with -apply), -updatepaths, and a
one-time -importposts <posts.db> migration.
Schema: Blogs.TTFolderPath and Posts.PostType are added by an idempotent
migration. On (BlogName, PostID) collisions, content columns are
overwritten while engagement columns (ByLikes, RootBlogName, RootURL,
HasNotesGathered, NotFound, NotesGatheredDateTime, Likes*) are preserved.
Co-Authored-By: Claude Opus 4.7 <[email protected]>
