Summary

• enforce the websearch response limit while consuming the response stream instead of buffering the full body first
• stop reading and cancel oversized response streams as soon as they cross the limit
• return HTML-to-Markdown conversion exceptions as model-visible webfetch failures

Test plan

• bun run test test/tool-websearch.test.ts test/tool-webfetch.test.ts from packages/core (24 passed)
• bun typecheck from packages/core
• pre-push bun turbo typecheck (23 packages passed)
• Prettier and git diff --check