Plugins that persist state have been writing into their own install tree
(<hermes home>/plugins/<name>/), which `hermes plugins update` git-pulls and
`hermes plugins remove` deletes — user data dies with the code that wrote it.
plugins/plugin_storage.py is the sanctioned home: plugin_data_dir(name) gives
one data root per plugin under <hermes home>/plugin-data/<name>/ (profile-
aware, created on first use, names validated against traversal), and
plugin_db(name) opens a WAL-mode SQLite database inside it. Secrets stay on
the existing secret-scope path — this is state, not credentials.
hermes-achievements, the in-tree offender, converts with a legacy-file
migration on first read.
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