feat(ai): few-shot exemplars + sticky Ollama preference

- Few-shot injection on /insights/generate/agentic: compresses prior
  training_messages into trajectory blocks (tool calls + result summaries)
  and injects into the system prompt. Hardcoded default ids with optional
  request override.
- New fewshot_source_ids column on photo_insights (+ migration) to track
  which exemplars influenced a given row, for downstream training-set
  filtering. Chat amend rows stamp None with a lineage note.
- Ollama client now remembers which server (primary/fallback) most
  recently succeeded and tries it first on the next call, via a shared
  Arc<AtomicBool>. Avoids re-404ing the primary on every agent iteration
  when the chosen model only lives on the fallback.
- Demote noisy logs: daily_summary "Summary match" lines to debug;
  inner chat_with_tools non-2xx body log from error to warn (outer
  layer owns the terminal-error signal).
- Drift-guard tests for summarize_tool_result covering the success /
  empty / error / unknown shape for every tool.
- Tidy: three pre-existing clippy warnings cleaned up.

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

src/database/daily_summary_dao.rs

@@ -268,7 +268,7 @@ impl DailySummaryDao for SqliteDailySummaryDao {
                 .into_iter()
                 .take(limit)
                 .map(|(similarity, summary)| {
-                    log::info!(
+                    log::debug!(
                         "Summary match: similarity={:.3}, date={}, contact={}, summary=\"{}\"",
                         similarity,
                         summary.date,
@@ -388,7 +388,7 @@ impl DailySummaryDao for SqliteDailySummaryDao {
                 .into_iter()
                 .take(limit)
                 .map(|(combined, similarity, days, summary)| {
-                    log::info!(
+                    log::debug!(
                         "Summary match: combined={:.3} (sim={:.3}, days={}), date={}, contact={}, summary=\"{}\"",
                         combined,
                         similarity,

src/database/insights_dao.rs

@@ -38,6 +38,16 @@ pub trait InsightDao: Sync + Send {
         file_path: &str,
     ) -> Result<Vec<PhotoInsight>, DbError>;
 
+    /// Fetch a single insight by primary key, regardless of `is_current`.
+    /// Used by the few-shot injection flow where the caller picks specific
+    /// historical insights (which may have been superseded) as training
+    /// exemplars for a fresh generation.
+    fn get_insight_by_id(
+        &mut self,
+        context: &opentelemetry::Context,
+        insight_id: i32,
+    ) -> Result<Option<PhotoInsight>, DbError>;
+
     fn delete_insight(
         &mut self,
         context: &opentelemetry::Context,
@@ -198,6 +208,25 @@ impl InsightDao for SqliteInsightDao {
         .map_err(|_| DbError::new(DbErrorKind::QueryError))
     }
 
+    fn get_insight_by_id(
+        &mut self,
+        context: &opentelemetry::Context,
+        insight_id: i32,
+    ) -> Result<Option<PhotoInsight>, DbError> {
+        trace_db_call(context, "query", "get_insight_by_id", |_span| {
+            use schema::photo_insights::dsl::*;
+
+            let mut connection = self.connection.lock().expect("Unable to get InsightDao");
+
+            photo_insights
+                .find(insight_id)
+                .first::<PhotoInsight>(connection.deref_mut())
+                .optional()
+                .map_err(|_| anyhow::anyhow!("Query error"))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
     fn delete_insight(
         &mut self,
         context: &opentelemetry::Context,

src/database/models.rs

@@ -102,6 +102,12 @@ pub struct InsertPhotoInsight {
     pub training_messages: Option<String>,
     /// `"local"` (Ollama with images) | `"hybrid"` (local vision + OpenRouter chat).
     pub backend: String,
+    /// JSON array of insight ids whose `training_messages` were compressed
+    /// and injected into the system prompt as few-shot exemplars when this
+    /// row was generated. `None` means no few-shot was used (pristine
+    /// generation). Used downstream to filter out contaminated rows when
+    /// assembling an unbiased training / evaluation set.
+    pub fewshot_source_ids: Option<String>,
 }
 
 #[derive(Serialize, Queryable, Clone, Debug)]
@@ -119,6 +125,7 @@ pub struct PhotoInsight {
     pub approved: Option<bool>,
     /// `"local"` (Ollama with images) | `"hybrid"` (local vision + OpenRouter chat).
     pub backend: String,
+    pub fewshot_source_ids: Option<String>,
 }
 
 // --- Libraries ---

src/database/schema.rs

@@ -143,6 +143,7 @@ diesel::table! {
         training_messages -> Nullable<Text>,
         approved -> Nullable<Bool>,
         backend -> Text,
+        fewshot_source_ids -> Nullable<Text>,
     }
 }