refactor(core): compact human log format, quieter lock lifecycle, nonzero_summary helper

Three quality-of-life improvements to reduce log noise and improve readability:

1. logging.rs: Add CompactHumanFormat for stderr tracing output. Replaces the
   default format with a minimal 'HH:MM:SS LEVEL  message key=value' layout —
   no span context, no full timestamps, no target module. The JSON file log
   layer is unaffected. This makes watching 'lore sync' output much cleaner.

2. lock.rs: Downgrade AppLock acquire/release messages from info! to debug!.
   Lock lifecycle events (acquired new, acquired existing, released) are
   operational bookkeeping that clutters normal output. They remain visible
   at -vv verbosity for troubleshooting.

3. ingestion/mod.rs: Add nonzero_summary() utility that formats named counters
   as a compact middle-dot-separated string, suppressing zero values. Produces
   output like '42 fetched · 3 labels · 12 notes' instead of verbose key=value
   structured fields. Returns 'nothing to update' when all values are zero.

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

src/ingestion/mod.rs

@@ -14,6 +14,22 @@ pub use merge_requests::{
     ingest_merge_requests,
 };
 pub use mr_discussions::{IngestMrDiscussionsResult, ingest_mr_discussions};
+/// Format a set of named counters as a compact human-readable summary,
+/// filtering out zero values and joining with middle-dot separators.
+/// Returns `"nothing to update"` when all values are zero.
+pub(crate) fn nonzero_summary(pairs: &[(&str, usize)]) -> String {
+    let parts: Vec<String> = pairs
+        .iter()
+        .filter(|(_, v)| *v > 0)
+        .map(|(k, v)| format!("{v} {k}"))
+        .collect();
+    if parts.is_empty() {
+        "nothing to update".to_string()
+    } else {
+        parts.join(" \u{b7} ")
+    }
+}
+
 pub use orchestrator::{
     DrainResult, IngestMrProjectResult, IngestProjectResult, ProgressCallback, ProgressEvent,
     ingest_project_issues, ingest_project_issues_with_progress, ingest_project_merge_requests,