feat(sync): Wire progress callbacks through sync pipeline stages

The sync command's stage spinners now show real-time aggregate progress
for each pipeline phase instead of static "syncing..." messages.

- Add `progress_callback` parameter to `run_embed` and
  `run_generate_docs` so callers can receive `(processed, total)` updates
- Add `stage_bar` parameter to `run_ingest` for aggregate progress
  across concurrently-ingested projects using shared AtomicUsize counters
- Update `stage_spinner` to use `{prefix}` for the `[N/M]` label,
  allowing `{msg}` to be updated independently with progress details
- Thread `ProgressBar` clones into each concurrent project task so
  per-entity progress (fetch, discussions, events) is reflected on the
  aggregate spinner
- Pass `None` for progress callbacks at standalone CLI entry points
  (handle_ingest, handle_generate_docs, handle_embed) to preserve
  existing behavior when commands are run outside of sync

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

src/main.rs

@@ -501,6 +501,7 @@ async fn handle_ingest(
                     force,
                     full,
                     display,
+                    None,
                 )
                 .await?;
 
@@ -527,6 +528,7 @@ async fn handle_ingest(
                     force,
                     full,
                     display,
+                    None,
                 )
                 .await?;
 
@@ -537,6 +539,7 @@ async fn handle_ingest(
                     force,
                     full,
                     display,
+                    None,
                 )
                 .await?;
 
@@ -1225,7 +1228,7 @@ async fn handle_generate_docs(
 ) -> Result<(), Box<dyn std::error::Error>> {
     let config = Config::load(config_override)?;
 
-    let result = run_generate_docs(&config, args.full, args.project.as_deref())?;
+    let result = run_generate_docs(&config, args.full, args.project.as_deref(), None)?;
     if robot_mode {
         print_generate_docs_json(&result);
     } else {
@@ -1242,7 +1245,7 @@ async fn handle_embed(
     let config = Config::load(config_override)?;
     let full = args.full && !args.no_full;
     let retry_failed = args.retry_failed && !args.no_retry_failed;
-    let result = run_embed(&config, full, retry_failed).await?;
+    let result = run_embed(&config, full, retry_failed, None).await?;
     if robot_mode {
         print_embed_json(&result);
     } else {