* Plugins: clean up channel config on uninstall
`openclaw plugins uninstall` only removed `plugins.*` entries but left
`channels.<id>` config behind, causing errors when the gateway
referenced a channel whose plugin no longer existed.
Now `removePluginFromConfig` also deletes the matching
`channels.<pluginId>` entry (exact match only), and the CLI
previews/reports the removal. Shared config keys like `defaults`
and `modelByChannel` are guarded from accidental removal.
* Plugins: sync uninstall preview with channel cleanup
* fix: clean up channel config on uninstall (#35915) (thanks @wbxl2000)
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Co-authored-by: George Zhang <georgezhangtj97@gmail.com>
