[codex] Harden Windows memory dump parsing

[tianmind-studio]

Summary

• Skip Markdown code fence lines when parsing pasted ChatGPT/Claude memory dumps.
• Strip additional common pasted list markers, including em dash, triangular bullet, and hyphen bullet variants.
• Add focused coverage for fenced dumps and richer pasted list markers.
• Format the touched fence test with the current Windows app dev dependencies.

Why

Windows users often copy memory lists from chat surfaces that wrap content in Markdown fences or use typographic bullets/dashes. The existing parser could keep ``` fences as bogus memories and leave some common marker characters in the imported text.

Refresh

• Rebased on main at 1a5824403b.
• Current head: 1d014a789c.

Validation

• vitest run src/main/memoryImport/parse.test.ts -> 1 file passed, 8 tests passed
• npm run typecheck -> passed
• prettier --check src/main/memoryImport/parse.ts src/main/memoryImport/parse.test.ts -> passed
• git diff --check origin/main...HEAD
• scripts/pre-commit with the backend Windows venv and local Dart SDK on PATH