Closed the four follow-up review findings in the Markdown editor.
- Prevented a second upload from nesting inside an existing Radial image after its selected alt text is edited.
- Sanitized filename-derived alt text once so the image record, Markdown, and selected range agree.
- Made file drops insert at CodeMirror's pointer-derived drop position.
- Preserved the textarea's complete selection when the delayed CodeMirror chunk takes over.
- Added component coverage for edited-alt insertion, drop positioning, and selection transfer, plus filename sanitization cases.
Checks passed: pnpm codegen, pnpm typecheck, pnpm lint, pnpm test, pnpm build, and a second codegen with generated output unchanged. The full UI suite passed 474 tests.
Branch: radial/impl-da42ce2a5b79
Commit: d61069eebf5201e734042dfeadc2c2899cb136f5
Pull request: https://tangled.org/disnetdev.com/radial/pulls/7
Remaining risk: CodeMirror interaction coverage runs in jsdom; pointer geometry, mobile keyboard behavior, and real IME behavior still need live-browser acceptance.