* fix: Remove state_key: null from Seshat search results
Seshat includes "state_key": null for non-state events, which causes
matrix-js-sdk to incorrectly treat them as state events. This prevents
encrypted messages from rendering properly in search results.
This fix removes the null state_key from search results and context
events before passing them to the SDK.
* test: cover local search null state_key edge cases
* test: satisfy strict types in searching coverage test
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Co-authored-by: David Baker <dbkr@users.noreply.github.com>
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