test: support pi-vim wrapper integration

[lajarre]

summary

• Add wrapper-facing coverage for the editor surface later decorators rely on.
• Add script/image-attachments-e2e.ts for the supported order: pi-vim first, @jordyvd/pi-image-attachments second.
• Document wrapper load order and why feat: chain onto previously installed editor factory (#3935) #18/fix: harden PR18 editor delegation #21 previous-editor delegation is not used here.
• Ignore .tmp/ in lint configs so scratch files do not affect hooks.

This supersedes #18 and #21 with pi-vim-first wrapper support only. The inverse load order is not part of this change.

verification

• npm run lint
• npm run typecheck
• npm test — 500 passed
• npm run pack:check
• node --import tsx/esm script/image-attachments-e2e.ts
• pre-push hook: npm run check and npm run pack:check