CoS tip: read JSON ACP resource links as text (#51069)

[kvnloo]

Origin

anomalyco#51069

Intent

ACP resource_link blocks with application/json or *+json MIME (e.g. .ipynb) must be ingested as text so notebook/JSON content reaches the model — not left as opaque binary file attachments.

Proof (fail → pass)

cd packages/opencode && bun test test/acp/content.test.ts -t "JSON notebook is read as text|PDF remains a file attachment"
# NEGATIVE: 1 pass / 1 fail (JSON mime stays application/x-ipynb+json)
# GREEN: 2 pass / 0 fail
# restore: 1 pass / 1 fail

Notes

• Base: dev
• github_writes_origin=0
• Codex promote: parked