evidence.sh prints image markdown for an uploaded .html file

[fairchild]

Found on PR #1615 (Closes #1613), outside its fence.

scripts/evidence.sh:275 (re-verify) prints a ![name](url) image-markdown hint to stderr after every upload. Since #1615, .html uploads are pages, and the hint tells a caller to embed one as an image, which renders nothing. The hint should follow the file's type: image markdown for images and video, a plain link for .html and .txt.

Requested Evidence

• Diff: the hint branches on the uploaded extension
• bash -n scripts/evidence.sh passes

Orchestrator note (workspaces)