MCP tool results: _meta handling fixed and capped, late-bind request ids ignored

What

MCP (Model Context Protocol) servers give Claude extra tools. Their results can carry extra details in a field called _meta.

• The _meta on a tool result is now built by a shared helper instead of copying a single flag.
• Stripping _meta from text blocks never worked because the code checked the wrong value. That is fixed.
• If the text blocks' _meta is over a character limit, or cannot be turned into JSON, it is left off the kept result.
• When reading a request id, ids starting with late-bind- are now ignored.

Why

Large _meta from an MCP server no longer bloats the results Claude Code keeps, and requests are matched up differently when they use late-bind ids.