Teknium ruled the post-admission consumer hook (#129958) must fail OPEN, so
reshape the salvaged implementation into one small seam:
- `{"action": "handled", "reply": str|None}` is the only decisive result;
None, any other value, a raising callback or a timeout runs the ordinary
agent turn. One buggy plugin can no longer blackhole every inbound
message on a profile (the cherry-picked version failed closed on any
exception or malformed return from ANY registered callback).
- Fire under the message's ROUTED profile scope. The receiving bot's
handler binds the transport home so auth can read its .env; when that
bot serves a chat for another profile, the ambient scope at the hook was
the wrong profile and that profile's consumers never ran.
- Snapshot-only payload (session_key, platform, source dict, message_id,
text): no live gateway runner / session store handles, so the plugin
isolation host needs no HOST_DEGRADED_HOOKS entry.
- Bounded by plugins.hook_callback_timeout (fail-open) instead of the
fail-closed policy-hook set; the required-but-discarded receipt, alias
table, destination snapshot/restore machinery and hard-coded English
failure notice are gone.
- Tests trimmed to three invariants through the real _handle_message and
real plugin dispatch: consume path, raise path proceeds, routed profile
scope bound.
be5481690d