Skill: Tool renames (#296383)

* Add tool-rename-deprecation skill for legacy name backward compat

* Fix deprecated name resolution for namespaced tool references in toolsets

When a tool belongs to a toolset and has legacyToolReferenceFullNames,
the deprecated names map now includes the namespaced form (e.g.
vscode/openSimpleBrowser → vscode/openIntegratedBrowser). Previously
only the bare name was mapped, so agent files using the full
toolSet/toolName path got 'Unknown tool' instead of the rename hint.