chore(plugins): add [integrity] SHA-256 hashes for all hook scripts

The daemon's `manifest_missing_integrity_hooks` check (#3804) hard-fails
any registry install whose plugin.toml declares hooks but lacks an
[integrity] entry for each one. All 11 plugins under plugins/ had the
[hooks] table but were missing [integrity], so `librefang plugin install
<name>` would error after download with "missing [integrity] hashes for
hook script(s): ...".

Compute and pin SHA-256 over each `hooks/*.py` under every plugin dir.
The mempalace-indexer entries were already present and are unchanged
(reordered alphabetically by the regenerator).

Verified each plugin.toml still parses (Python tomllib).

plugins/episodic-memory/plugin.toml

@@ -35,3 +35,7 @@ description = "Segmentación y recuerdo de memoria por episodios para continuida
 [i18n.fr]
 name = "Mémoire épisodique"
 description = "Segmentation et rappel de mémoire par épisodes pour une continuité de contexte entre conversations."
+
+[integrity]
+"hooks/after_turn.py" = "b3adcfd2d5032a849a69722f64260802b70b01f54719e67cbe46db4e4214d9f3"
+"hooks/ingest.py" = "c33c0888b86a6f2058ceb1a0062420fd433a5c971e4abc44faccb1b775b0c1f5"