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(),