Problem

Multiple MCP servers can register tools with the same name. Current behavior is silent overwrite, first one registered wins.

Context

Namespacing tools by server (mezmo_search, k8_get_pods) would prevent collisions and make mcp_filter globs more useful (mezmo_*, k8_get_*).

There are backwards compat concerns though:

• System prompts reference tool names verbatim ("run 'x' before 'y'"), renaming breaks those
• mcp_filter matches on explicit tool names, existing configs would need updating
• Need to think about how namespaces are defined in config so tool names don't get unreasonably long

Needs some strategy before we just start prefixing things.

Raised by @dominic-mcallister-logdna in PR #181.