personas: elevate to server with per-persona fact scoping

Move personas off the mobile client into ImageApi as first-class
records, and scope entity_facts by persona so each one builds its own
voice over a shared entity graph. The new include_all_memories flag
lets a persona opt back into the full hive-mind pool for human
browsing of /knowledge/*; agentic generation always stays in-voice.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ai/handlers.rs

@@ -48,6 +48,11 @@ pub struct GeneratePhotoInsightRequest {
     /// falls back to `DEFAULT_FEWSHOT_INSIGHT_IDS`.
     #[serde(default)]
     pub fewshot_insight_ids: Option<Vec<i32>>,
+    /// Active persona id for this generation. New facts are tagged with
+    /// it (`entity_facts.persona_id`); recall during the agentic loop is
+    /// scoped to it. Defaults to `"default"` when absent.
+    #[serde(default)]
+    pub persona_id: Option<String>,
 }
 
 #[derive(Debug, Deserialize)]
@@ -376,6 +381,13 @@ pub async fn generate_agentic_insight_handler(
             .collect()
     };
 
+    let persona_id = request
+        .persona_id
+        .clone()
+        .filter(|s| !s.trim().is_empty())
+        .unwrap_or_else(|| "default".to_string());
+    span.set_attribute(KeyValue::new("persona_id", persona_id.clone()));
+
     let result = insight_generator
         .generate_agentic_insight_for_photo(
             &normalized_path,
@@ -390,6 +402,7 @@ pub async fn generate_agentic_insight_handler(
             request.backend.clone(),
             fewshot_examples,
             fewshot_ids,
+            persona_id,
         )
         .await;
 
@@ -645,6 +658,10 @@ pub struct ChatTurnHttpRequest {
     /// semantics. Also seeds the bootstrap path when no insight exists.
     #[serde(default)]
     pub system_prompt: Option<String>,
+    /// Active persona id for this turn. New facts/recalls scope to it.
+    /// Defaults to `"default"` when missing.
+    #[serde(default)]
+    pub persona_id: Option<String>,
     #[serde(default)]
     pub amend: bool,
     /// When true, force the bootstrap path even if an insight already
@@ -707,6 +724,7 @@ pub async fn chat_turn_handler(
         min_p: request.min_p,
         max_iterations: request.max_iterations,
         system_prompt: request.system_prompt.clone(),
+        persona_id: request.persona_id.clone(),
         amend: request.amend,
         regenerate: request.regenerate,
     };
@@ -923,6 +941,7 @@ pub async fn chat_stream_handler(
         min_p: request.min_p,
         max_iterations: request.max_iterations,
         system_prompt: request.system_prompt.clone(),
+        persona_id: request.persona_id.clone(),
         amend: request.amend,
         regenerate: request.regenerate,
     };