* Add configurable worktree root
Allow new Paseo worktrees to be created under a custom worktrees.root from config.json while preserving the existing PASEO_HOME/worktrees default. Thread the resolved root through create/list/archive/ownership flows, MCP/session paths, checkout metadata, schema, docs, and targeted tests.
* Address worktree root review feedback
Use the resolved Paseo worktree base when a custom PASEO_HOME is provided, and remove an unused worktreesRoot dependency from worktree list handling.
* Fix checkout worktree path test on Windows
Use platform-native paths in the custom PASEO_HOME regression test so Windows CI compares against the same resolved root shape as production code.
* Clarify optional worktrees config docs
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Co-authored-by: Mohamed Boudra <boudra.moha@gmail.com>