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/conversation-logger/plugin.toml

@@ -34,3 +34,6 @@ description = "Registra todas las conversaciones en archivos JSONL para auditor
 [i18n.fr]
 name = "Journal de conversations"
 description = "Enregistre toutes les conversations en JSONL pour audit, analytics et débogage."
+
+[integrity]
+"hooks/after_turn.py" = "19a008af65e6797186ac0cc5b88e6d3c889fb1e312a099d65b9e10ee749eb65e"