feat(timeline): add entity-direct seeding and round-robin evidence selection

Enhance the timeline command with two major improvements:

1. Entity-direct seeding syntax (bypass search):
   lore timeline issue:42    # Timeline for specific issue
   lore timeline i:42        # Short form
   lore timeline mr:99       # Timeline for specific MR
   lore timeline m:99        # Short form

   This directly resolves the entity and gathers ALL its discussions without
   requiring search/embedding. Useful when you know exactly which entity you want.

2. Round-robin evidence note selection:
   Previously, evidence notes were taken in FTS rank order, which could result
   in all notes coming from a single high-traffic discussion. Now we:
   - Fetch 5x the requested limit (or minimum 50)
   - Group notes by discussion_id
   - Select round-robin across discussions
   - This ensures diverse evidence from multiple conversations

API changes:
- Renamed total_events_before_limit -> total_filtered_events (clearer semantics)
- Added resolve_entity_by_iid() in timeline.rs for IID-based entity resolution
- Added seed_timeline_direct() in timeline_seed.rs for search-free seeding
- Added round_robin_select_by_discussion() helper function

The entity-direct mode uses search_mode: "direct" to distinguish from
"hybrid" or "lexical" search modes in the response metadata.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/cli/commands/timeline.rs

@@ -175,7 +175,7 @@ pub async fn run_timeline(config: &Config, params: &TimelineParams) -> Result<Ti
         query: params.query.clone(),
         search_mode: seed_result.search_mode,
         events,
-        total_events_before_limit: total_before_limit,
+        total_filtered_events: total_before_limit,
         seed_entities: seed_result.seed_entities,
         expanded_entities: expand_result.expanded_entities,
         unresolved_references: expand_result.unresolved_references,
@@ -342,7 +342,7 @@ fn format_entity_ref(entity_type: &str, iid: i64) -> String {
 /// Render timeline as robot-mode JSON in {ok, data, meta} envelope.
 pub fn print_timeline_json_with_meta(
     result: &TimelineResult,
-    total_events_before_limit: usize,
+    total_filtered_events: usize,
     depth: u32,
     include_mentions: bool,
     fields: Option<&[String]>,
@@ -355,7 +355,7 @@ pub fn print_timeline_json_with_meta(
             expansion_depth: depth,
             include_mentions,
             total_entities: result.seed_entities.len() + result.expanded_entities.len(),
-            total_events: total_events_before_limit,
+            total_events: total_filtered_events,
             evidence_notes_included: count_evidence_notes(&result.events),
             discussion_threads_included: count_discussion_threads(&result.events),
             unresolved_references: result.unresolved_references.len(),

src/core/timeline.rs

@@ -164,9 +164,10 @@ pub struct TimelineResult {
     /// The search mode actually used for seeding (e.g. "hybrid", "lexical", "lexical (hybrid fallback)").
     pub search_mode: String,
     pub events: Vec<TimelineEvent>,
-    /// Total events before the `--limit` was applied (for meta.total_events vs meta.showing).
+    /// Total events after filters (e.g., --since) but before --limit was applied.
+    /// Use this to show "showing X of Y filtered events".
     #[serde(skip)]
-    pub total_events_before_limit: usize,
+    pub total_filtered_events: usize,
     pub seed_entities: Vec<EntityRef>,
     pub expanded_entities: Vec<ExpandedEntityRef>,
     pub unresolved_references: Vec<UnresolvedRef>,

src/core/timeline_seed.rs

@@ -260,6 +260,9 @@ fn resolve_documents_to_entities(
 }
 
 /// Find evidence notes: FTS5-matched discussion notes that provide context.
+///
+/// Uses round-robin selection across discussions to ensure diverse evidence
+/// rather than all notes coming from a single high-traffic discussion.
 fn find_evidence_notes(
     conn: &Connection,
     fts_query: &str,
@@ -267,6 +270,10 @@ fn find_evidence_notes(
     since_ms: Option<i64>,
     max_evidence: usize,
 ) -> Result<Vec<TimelineEvent>> {
+    // Fetch extra rows to enable round-robin across discussions.
+    // We'll select from multiple discussions in rotation.
+    let fetch_limit = (max_evidence * 5).max(50);
+
     let sql = r"
         SELECT n.id AS note_id, n.body, n.created_at, n.author_username,
                disc.id AS discussion_id,
@@ -286,7 +293,7 @@ fn find_evidence_notes(
 
     let mut stmt = conn.prepare(sql)?;
     let rows = stmt.query_map(
-        rusqlite::params![fts_query, project_id, since_ms, max_evidence as i64],
+        rusqlite::params![fts_query, project_id, since_ms, fetch_limit as i64],
         |row| {
             Ok((
                 row.get::<_, i64>(0)?,            // note_id
@@ -331,25 +338,84 @@ fn find_evidence_notes(
             }
         };
 
-        events.push(TimelineEvent {
-            timestamp: created_at,
-            entity_type: parent_type,
-            entity_id: parent_entity_id,
-            entity_iid: iid,
-            project_path,
-            event_type: TimelineEventType::NoteEvidence {
-                note_id,
-                snippet,
-                discussion_id: Some(discussion_id),
+        events.push((
+            discussion_id,
+            TimelineEvent {
+                timestamp: created_at,
+                entity_type: parent_type,
+                entity_id: parent_entity_id,
+                entity_iid: iid,
+                project_path,
+                event_type: TimelineEventType::NoteEvidence {
+                    note_id,
+                    snippet,
+                    discussion_id: Some(discussion_id),
+                },
+                summary: format!("Note by {}", author.as_deref().unwrap_or("unknown")),
+                actor: author,
+                url: None,
+                is_seed: true,
             },
-            summary: format!("Note by {}", author.as_deref().unwrap_or("unknown")),
-            actor: author,
-            url: None,
-            is_seed: true,
-        });
+        ));
     }
 
-    Ok(events)
+    // Round-robin selection across discussions for diverse evidence
+    Ok(round_robin_select_by_discussion(events, max_evidence))
+}
+
+/// Round-robin select events across discussions to ensure diverse evidence.
+///
+/// Groups events by discussion_id, then iterates through discussions in order,
+/// taking one event from each until the limit is reached.
+fn round_robin_select_by_discussion(
+    events: Vec<(i64, TimelineEvent)>,
+    max_evidence: usize,
+) -> Vec<TimelineEvent> {
+    use std::collections::HashMap;
+
+    if events.is_empty() || max_evidence == 0 {
+        return Vec::new();
+    }
+
+    // Group events by discussion_id, preserving order within each group
+    let mut by_discussion: HashMap<i64, Vec<TimelineEvent>> = HashMap::new();
+    let mut discussion_order: Vec<i64> = Vec::new();
+
+    for (discussion_id, event) in events {
+        if !by_discussion.contains_key(&discussion_id) {
+            discussion_order.push(discussion_id);
+        }
+        by_discussion.entry(discussion_id).or_default().push(event);
+    }
+
+    // Round-robin selection
+    let mut result = Vec::with_capacity(max_evidence);
+    let mut indices: Vec<usize> = vec![0; discussion_order.len()];
+
+    'outer: loop {
+        let mut made_progress = false;
+
+        for (disc_idx, &discussion_id) in discussion_order.iter().enumerate() {
+            let notes = by_discussion.get(&discussion_id).unwrap();
+            let note_idx = indices[disc_idx];
+
+            if note_idx < notes.len() {
+                result.push(notes[note_idx].clone());
+                indices[disc_idx] += 1;
+                made_progress = true;
+
+                if result.len() >= max_evidence {
+                    break 'outer;
+                }
+            }
+        }
+
+        if !made_progress {
+            break;
+        }
+    }
+
+    result
 }
 
 #[cfg(test)]