ai: add llamacpp backend (llama-swap) as third LLM client

Wires a new LlamaCppClient (OpenAI-compatible /v1 wire format) alongside
OllamaClient and OpenRouterClient. Per-slot routing for chat/vision/embed
via env (LLAMA_SWAP_URL + *_MODEL vars); capability inference uses an
env allowlist since /v1/models doesn't report modality.

InsightGenerator + InsightChatService gain three-way dispatch on
chat_backend = "local" | "hybrid" | "llamacpp". Hybrid and llamacpp
share the describe-then-inline path (text-only chat after a separate
vision describe). HYBRID_VISION_BACKEND=llamacpp lets hybrid route its
describe pass through llama-swap's vision slot while chat still goes
to OpenRouter.

Cross-replay matrix added (validate_cross_replay): local<->llamacpp
and hybrid<->llamacpp allowed; local->hybrid and llamacpp->hybrid
rejected. New /insights/llamacpp/models handler mirrors the OpenRouter
shape.

src/state.rs

@@ -2,6 +2,7 @@ use crate::ai::apollo_client::ApolloClient;
 use crate::ai::clip_client::ClipClient;
 use crate::ai::face_client::FaceClient;
 use crate::ai::insight_chat::{ChatLockMap, InsightChatService};
+use crate::ai::llamacpp::LlamaCppClient;
 use crate::ai::openrouter::OpenRouterClient;
 use crate::ai::{InsightGenerator, OllamaClient, SmsApiClient};
 use crate::database::{
@@ -62,6 +63,16 @@ pub struct AppState {
     /// Curated list of OpenRouter model ids exposed to clients. Sourced from
     /// `OPENROUTER_ALLOWED_MODELS` (comma-separated). Empty when unset.
     pub openrouter_allowed_models: Vec<String>,
+    /// `None` when `LLAMA_SWAP_URL` is not configured. Consulted only when a
+    /// request explicitly opts into `backend=llamacpp`. Same shape as the
+    /// `openrouter` slot — present here so handlers can route to it without
+    /// threading through the generator.
+    #[allow(dead_code)]
+    pub llamacpp: Option<Arc<LlamaCppClient>>,
+    /// Curated list of llama-swap model ids exposed to clients. Sourced from
+    /// `LLAMA_SWAP_ALLOWED_MODELS` (comma-separated). Empty when unset; the
+    /// server then falls back to `LLAMA_SWAP_PRIMARY_MODEL`.
+    pub llamacpp_allowed_models: Vec<String>,
     pub sms_client: SmsApiClient,
     pub insight_generator: InsightGenerator,
     /// Chat continuation service. Hold an Arc so handlers can clone cheaply.
@@ -105,6 +116,8 @@ impl AppState {
         ollama: OllamaClient,
         openrouter: Option<Arc<OpenRouterClient>>,
         openrouter_allowed_models: Vec<String>,
+        llamacpp: Option<Arc<LlamaCppClient>>,
+        llamacpp_allowed_models: Vec<String>,
         sms_client: SmsApiClient,
         insight_generator: InsightGenerator,
         insight_chat: Arc<InsightChatService>,
@@ -145,6 +158,8 @@ impl AppState {
             ollama,
             openrouter,
             openrouter_allowed_models,
+            llamacpp,
+            llamacpp_allowed_models,
             sms_client,
             insight_generator,
             insight_chat,
@@ -186,6 +201,9 @@ impl Default for AppState {
         let openrouter = build_openrouter_from_env();
         let openrouter_allowed_models = parse_openrouter_allowed_models();
 
+        let llamacpp = build_llamacpp_from_env();
+        let llamacpp_allowed_models = parse_llamacpp_allowed_models();
+
         let sms_api_url =
             env::var("SMS_API_URL").unwrap_or_else(|_| "http://localhost:8000".to_string());
         let sms_api_token = env::var("SMS_API_TOKEN").ok();
@@ -250,6 +268,7 @@ impl Default for AppState {
         let insight_generator = InsightGenerator::new(
             ollama.clone(),
             openrouter.clone(),
+            llamacpp.clone(),
             sms_client.clone(),
             apollo_client.clone(),
             insight_dao.clone(),
@@ -273,6 +292,7 @@ impl Default for AppState {
             Arc::new(insight_generator.clone()),
             ollama.clone(),
             openrouter.clone(),
+            llamacpp.clone(),
             insight_dao.clone(),
             chat_locks,
         ));
@@ -294,6 +314,8 @@ impl Default for AppState {
             ollama,
             openrouter,
             openrouter_allowed_models,
+            llamacpp,
+            llamacpp_allowed_models,
             sms_client,
             insight_generator,
             insight_chat,
@@ -335,6 +357,50 @@ fn parse_openrouter_allowed_models() -> Vec<String> {
         .collect()
 }
 
+/// Build a `LlamaCppClient` from environment variables. Returns `None` when
+/// `LLAMA_SWAP_URL` is unset (the llamacpp backend is then unavailable and
+/// requests for it return a clear error). The slot ids default to the
+/// names the bundled `llama-swap/config.yaml` uses — `chat` / `vision` /
+/// `embed` — so a minimal deploy only needs to set `LLAMA_SWAP_URL`.
+fn build_llamacpp_from_env() -> Option<Arc<LlamaCppClient>> {
+    let base_url = env::var("LLAMA_SWAP_URL").ok()?;
+    let primary_model = env::var("LLAMA_SWAP_PRIMARY_MODEL").ok();
+    let mut client = LlamaCppClient::new(Some(base_url), primary_model);
+    if let Ok(model) = env::var("LLAMA_SWAP_EMBEDDING_MODEL") {
+        client.set_embedding_model(model);
+    }
+    if let Ok(model) = env::var("LLAMA_SWAP_VISION_MODEL") {
+        client.set_vision_model(model);
+    }
+    client.set_vision_models(parse_llamacpp_vision_models());
+    Some(Arc::new(client))
+}
+
+/// Parse `LLAMA_SWAP_ALLOWED_MODELS` (comma-separated) into a vec. Used to
+/// drive `/insights/llamacpp/models`; empty when unset.
+fn parse_llamacpp_allowed_models() -> Vec<String> {
+    env::var("LLAMA_SWAP_ALLOWED_MODELS")
+        .unwrap_or_default()
+        .split(',')
+        .map(|s| s.trim().to_string())
+        .filter(|s| !s.is_empty())
+        .collect()
+}
+
+/// Parse `LLAMA_SWAP_VISION_MODELS` (comma-separated) — slot ids that report
+/// `has_vision = true` in capability lookups. The configured `vision_model`
+/// (default `vision`) is always considered vision-capable regardless of this
+/// list, so a deploy that only uses the default vision slot can leave it
+/// unset.
+fn parse_llamacpp_vision_models() -> Vec<String> {
+    env::var("LLAMA_SWAP_VISION_MODELS")
+        .unwrap_or_default()
+        .split(',')
+        .map(|s| s.trim().to_string())
+        .filter(|s| !s.is_empty())
+        .collect()
+}
+
 #[cfg(test)]
 impl AppState {
     /// Creates an AppState instance for testing with temporary directories
@@ -397,6 +463,7 @@ impl AppState {
         let insight_generator = InsightGenerator::new(
             ollama.clone(),
             None,
+            None,
             sms_client.clone(),
             apollo_client.clone(),
             insight_dao.clone(),
@@ -418,6 +485,7 @@ impl AppState {
             Arc::new(insight_generator.clone()),
             ollama.clone(),
             None,
+            None,
             insight_dao.clone(),
             chat_locks,
         ));
@@ -445,6 +513,8 @@ impl AppState {
             ollama,
             None,
             Vec::new(),
+            None,
+            Vec::new(),
             sms_client,
             insight_generator,
             insight_chat,