fix MCP tool name prefix stripping in callTool

[dgageot]

Tool calls when using the mcp catalog builtin tool would fail because a prefix is added to each tool in order to avoid conflicts

[docker-agent]

Assessment: 🟢 APPROVE

The fix correctly addresses the root cause: callTool was forwarding the prefixed tool name (e.g. github-official_get_issue) to the remote MCP server, which only knows the unprefixed name (get_issue), causing every catalog tool call to fail with "tool not found".

Fix analysis:

• strings.TrimPrefix(name, ts.name+"_") is the right primitive — it strips exactly one leading occurrence of <name>_ and is a no-op when ts.name is empty (unnamed toolsets) or the prefix is absent (misrouted calls)
• No off-by-one, no nil-dereference (Go strings are never nil), no double-stripping (TrimPrefix is not iterative)
• The ts.name != "" guard avoids any inadvertent behavior for unnamed toolsets

Test coverage is thorough — TestToolsAndCallToolRoundTrip and TestCallToolStripsToolsetNamePrefix together cover: named toolsets, unnamed toolsets, hyphenated catalog IDs, double-prefix tool names, and unprefixed calls forwarded unchanged.

No issues found in the changed lines.