Add configurable worktree root

* 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

---------

Co-authored-by: Mohamed Boudra <boudra.moha@gmail.com>

public-docs/worktrees.md

@@ -11,7 +11,7 @@ Each agent runs in its own git worktree, a separate directory on a separate bran
 
 ## Layout and workflow
 
-Worktrees live under `$PASEO_HOME/worktrees/`, grouped by a hash of the source checkout path. Each worktree gets a random slug; the branch name is chosen when you first launch an agent.
+Worktrees live under `$PASEO_HOME/worktrees/` by default, grouped by a hash of the source checkout path. You can change the base directory with `worktrees.root` in `config.json`. Each worktree gets a random slug; the branch name is chosen when you first launch an agent.
 
 ```
 ~/.paseo/worktrees/
@@ -20,6 +20,16 @@ Worktrees live under `$PASEO_HOME/worktrees/`, grouped by a hash of the source c
     └── bold-owl/
 ```
 
+With a custom root, Paseo keeps the same hashed layout under that directory:
+
+```json
+{
+  "worktrees": {
+    "root": "/mnt/fast/paseo-worktrees"
+  }
+}
+```
+
 1. Create a worktree, Paseo runs your setup hooks
 2. Launch an agent, a branch is created or assigned
 3. Review the diff against the base branch