AI spam classification: the model's opinion as one bounded spam signal, and the llm_prompt Sieve function (AI-1 to AI-28)

The classifier sends only the subject and text, between unforgeable markers
after the operator's prompt, to an OpenAI-compatible endpoint the operator
configured; nothing is preset. Its answer maps to an LLM_ tag whose score is
clamped (+5.0, -1.0 by default) and can never discard or reject on its own;
X-Spam-LLM is sanitized, encoded and folded, and a planted one is removed.
Failures, timeouts past the ceiling, a full slot or a paused model leave
mail flowing untagged. llm_prompt answers trusted scripts, and accounts
holding interactAi within an hourly limit. Redirects aren't followed and no
content or secret is logged. The limits live in inbuxa:AiLimits.
Acceptance tests 1 and 3 to 21; test 2 as the re-enabled shared llm case,
whose setup no longer waits on a rules file from a developer's own path;
test 22 written as the ignored ai_compat.

crates/jmap-proto/src/request/method.rs

@@ -45,6 +45,8 @@ pub enum MethodObject {
     MaskedEmail,
     // inbuxa: deleted accounts (UD-17)
     DeletedAccount,
+    // inbuxa: AI call limits
+    AiLimits,
 }
 
 impl MethodObject {
@@ -70,6 +72,7 @@ impl MethodObject {
             MethodObject::Registry(_) => Capability::Stalwart,
             MethodObject::MaskedEmail => Capability::FastmailMaskedEmail,
             MethodObject::DeletedAccount => Capability::Inbuxa,
+            MethodObject::AiLimits => Capability::Inbuxa,
         }
     }
 }
@@ -245,6 +248,8 @@ impl MethodName {
             (MethodFunction::Set, MethodObject::MaskedEmail) => "MaskedEmail/set",
             (MethodFunction::Get, MethodObject::DeletedAccount) => "inbuxa:DeletedAccount/get",
             (MethodFunction::Set, MethodObject::DeletedAccount) => "inbuxa:DeletedAccount/set",
+            (MethodFunction::Get, MethodObject::AiLimits) => "inbuxa:AiLimits/get",
+            (MethodFunction::Set, MethodObject::AiLimits) => "inbuxa:AiLimits/set",
             (method, MethodObject::Registry(obj)) => {
                 return Cow::Owned(format!("x:{}/{}", obj.as_str(), method.as_str()));
             }
@@ -368,6 +373,8 @@ impl MethodName {
             "MaskedEmail/set" => (MethodObject::MaskedEmail, MethodFunction::Set),
             "inbuxa:DeletedAccount/get" => (MethodObject::DeletedAccount, MethodFunction::Get),
             "inbuxa:DeletedAccount/set" => (MethodObject::DeletedAccount, MethodFunction::Set),
+            "inbuxa:AiLimits/get" => (MethodObject::AiLimits, MethodFunction::Get),
+            "inbuxa:AiLimits/set" => (MethodObject::AiLimits, MethodFunction::Set),
 
         ).or_else(|| {
             let (obj, fnc) = s.strip_prefix("x:")?.split_once('/')?;
@@ -420,6 +427,7 @@ impl Display for MethodObject {
             MethodObject::ShareNotification => "ShareNotification",
             MethodObject::MaskedEmail => "MaskedEmail",
             MethodObject::DeletedAccount => "inbuxa:DeletedAccount",
+            MethodObject::AiLimits => "inbuxa:AiLimits",
             MethodObject::Registry(obj) => {
                 f.write_str("x:")?;
                 return f.write_str(obj.as_str());