Watch history is ~150 separately encrypted chunk events; decrypting each one is
a serialized round-trip to the nip-07 extension (the key lives in the extension
and cannot be cached locally), so a full re-decrypt cost many seconds on EVERY
load. Chunk events are addressable/replaceable: an unchanged chunk keeps its
event id while a modified chunk republishes under a new id.
Add a persisted cache (watchHistoryDecryptCache.js) keyed by chunk event id. The
fetch path checks it before calling the extension and stores successful
decryptions, so reloads decrypt only the chunk(s) that actually changed
(typically one) and skip the extension for the rest — across sessions. Bounded
to 400 entries; cleared on logout alongside the conversation-key cache. The
cached plaintext is no more sensitive than the watch-history items already
persisted by the manager.
Adds watchHistoryDecryptCache.test.mjs (round-trip, persistence/re-hydrate,
bounds, clear).
Co-Authored-By: Claude Opus 4.8 <[email protected]>
