feat: implement lore explain command (bd-9lbr)

Auto-generates structured narratives for issues and MRs from local DB:
- EntitySummary with title, state, author, labels, status
- Key decisions heuristic (correlates state/label changes with nearby notes)
- Activity summary with event counts and time span
- Open threads detection (unresolved discussions)
- Related entities (closing MRs, related issues)
- Timeline of all events in chronological order

7 unit tests, robot-docs entry, autocorrect registry, CLI dispatch wired.

crates/lore-tui/src/lib.rs

@@ -71,6 +71,8 @@ pub struct LaunchOptions {
 /// 2. **Data readiness** — check whether the database has any entity data.
 ///    If empty, start on the Bootstrap screen; otherwise start on Dashboard.
 pub fn launch_tui(options: LaunchOptions) -> Result<()> {
+    let _options = options; // remaining fields (fresh, ascii, etc.) consumed in later phases
+
     // 1. Resolve database path.
     let db_path = lore::core::paths::get_db_path(None);
     if !db_path.exists() {
@@ -84,7 +86,7 @@ pub fn launch_tui(options: LaunchOptions) -> Result<()> {
     // 2. Open DB and run schema preflight.
     let db = db::DbManager::open(&db_path)
         .with_context(|| format!("opening database at {}", db_path.display()))?;
-    db.with_reader(|conn| schema_preflight(conn))?;
+    db.with_reader(schema_preflight)?;
 
     // 3. Check data readiness — bootstrap screen if empty.
     let start_on_bootstrap = db.with_reader(|conn| {