fix(mcp): clarify page asset reads

[suguanYang]

Summary

• Default SDK MCP knowhere_read_chunks display reads to assetUrlPolicy: "durable" when callers do not provide a policy, while preserving explicit policies and leaving targeted reads unset.
• Clarify that stdio file parse paths are local to the MCP server process, and document page screenshots under chunk metadata.pageAssets instead of image chunks.
• Add a patch changeset for @ontos-ai/knowhere-mcp.

Public API impact: no input schema change; this is an MCP wrapper default and documentation update.

Verification

• pnpm --filter @ontos-ai/knowhere-mcp test:ci -- src/tests/mcp.test.ts
• pnpm --filter @ontos-ai/knowhere-mcp typecheck
• pnpm --filter @ontos-ai/knowhere-mcp format:check
• pnpm --filter @ontos-ai/knowhere-mcp lint (passes with existing no-console warnings in src/stdio.ts)
• pnpm --filter @ontos-ai/knowhere-mcp build
• git diff --check

Checklist

• Tests were added or updated when behavior changed
• Public docs or examples were updated when needed
• A changeset was added when a release should be published