Code audit and issues

[DavidWells]

Return storage dispatch promises and support alwaysEnabled plugins with all: false.

This fixes two long-standing issues: #438 where setItem/removeItem were not awaitable, and #455 where plugins.all = false blocked enrichment plugins without an escape hatch.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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