feat: implement lore who — people intelligence commands (5 modes)

Add `lore who` command with 5 query modes answering collaboration questions
using existing DB data (280K notes, 210K discussions, 33K DiffNotes):

- Expert: who knows about a file/directory (DiffNote path analysis + MR breadth scoring)
- Workload: what is a person working on (assigned issues, authored/reviewing MRs, discussions)
- Active: what discussions need attention (unresolved resolvable, global/project-scoped)
- Overlap: who else is touching these files (dual author+reviewer role tracking)
- Reviews: what review patterns does a person have (prefix-based category extraction)

Includes migration 017 (5 composite indexes), CLI skeleton with clap conflicts_with
validation, robot JSON output with input+resolved_input reproducibility, human terminal
output, and 20 unit tests. All quality gates pass.

Closes: bd-1q8z, bd-34rr, bd-2rk9, bd-2ldg, bd-zqpf, bd-s3rc, bd-m7k1, bd-b51e,
bd-2711, bd-1rdi, bd-3mj2, bd-tfh3, bd-zibc, bd-g0d5

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/core/db.rs

@@ -52,6 +52,7 @@ const MIGRATIONS: &[(&str, &str)] = &[
         "016",
         include_str!("../../migrations/016_mr_file_changes.sql"),
     ),
+    ("017", include_str!("../../migrations/017_who_indexes.sql")),
 ];
 
 pub fn create_connection(db_path: &Path) -> Result<Connection> {