fix(mandrel-mcp-th): use workspace version for crates.io publishing

- Change version from hardcoded '0.1.0' to 'version.workspace = true'
- This ensures mandrel-mcp-th gets the correct version during release process
- Fixes crates.io publishing failure where version mismatch occurred

The release workflow expected mandrel-mcp-th@0.4.2 but crate was still at 0.1.0

Author: milliondreams

crates/mandrel-mcp-th/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mandrel-mcp-th"
-version = "0.1.0"
+version.workspace = true
 edition = "2021"
 authors = ["AI Assistant"]
 description = "Mandrel MCP Test Harness - Professional testing and reporting for MCP servers"