fix(uninstall): preserve user-installed Node.js

[taoyizhi68]

Problem

Uninstalling MicroClaw via the desktop Uninstall MicroClaw shortcut removes Node.js even when the user installed it themselves before installing MicroClaw. After uninstall, build.ps1 fails with:

ERROR: node.exe not found in any of:
  - C:\Program Files\nodejs
  - C:\Users\<user>\AppData\Local\Programs\nodejs
  - C:\Users\<user>\.openclaw-node
  - PATH (Get-Command node.exe)

The cause is in _msi_uninstall_node: it enumerates HKCU/HKLM Uninstall registry entries and runs msiexec /x on any entry whose DisplayName contains node.js, then _uninstall_clean_node rmtree's self.node_dir (typically C:\Program Files\nodejs). It has no way to tell apart "Node we installed" from "Node the user installed".

Fix

Add an ownership marker:

• install_node_windows writes ~/.openclaw/.node-installed-by-microclaw containing the install path on a successful MSI install.
• _uninstall_clean_node reads the marker:
  • No marker -> log "未发现 MicroClaw 安装 Node 的标记 — 保留用户自带的 Node.js", skip MSI uninstall, skip rmtree of self.node_dir, skip removing %APPDATA%\npm from PATH. The legacy ~/.openclaw-node directory is still cleaned (always ours).
  • Marker present -> only operate on the recorded path (+ legacy dirs).
• _msi_uninstall_node now requires the recorded path and additionally filters registry entries by InstallLocation, so unrelated Node MSIs are never touched.

Matrix

Node origin	Marker	Uninstall behavior
Installed by MicroClaw (MSI)	✅ written	Removed (as before)
User had Node at standard path; MicroClaw reused it	❌ none	Preserved
Non-standard user Node + MicroClaw also MSI-installed its own	✅ written for our path; user's path not in registry match	Only ours removed
Legacy zip-extracted ~/.openclaw-node	n/a	Always cleaned

Test

Repro before fix:

1. Manually install Node.js to C:\Program Files\nodejs
2. Install MicroClaw (it reuses the existing Node)
3. Click Uninstall MicroClaw desktop shortcut
4. build.ps1 -> fails: node.exe not found

After fix: step 4 succeeds; the user's Node.js remains intact.