Rename MCP tools to domain action names

[wpscholar]

Summary

• Rename public MCP tool slugs from verb-first hyphen names to domain/action underscore names like wp-forge-content_search and wp-forge-comment_save.
• Consolidate plugin activation/deactivation into wp-forge-plugin_set_status with status: active|inactive.
• Update README, admin copy, unit expectations, and integration endpoint calls for the new tool names.

Validation

• composer test
• node --check tests/integration/mcp-endpoint.mjs

Note: full Playground integration execution was not run because this pass did not start the WordPress Playground server.

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