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/core/logging.rs

@@ -1,7 +1,45 @@
+use std::fmt;
 use std::fs;
 use std::path::Path;
 
 use tracing_subscriber::EnvFilter;
+use tracing_subscriber::fmt::format::{FormatEvent, FormatFields};
+use tracing_subscriber::registry::LookupSpan;
+
+/// Compact stderr formatter: `HH:MM:SS LEVEL  message key=value`
+///
+/// No span context, no full timestamps, no target — just the essentials.
+/// The JSON file log is unaffected (it uses its own layer).
+pub struct CompactHumanFormat;
+
+impl<S, N> FormatEvent<S, N> for CompactHumanFormat
+where
+    S: tracing::Subscriber + for<'a> LookupSpan<'a>,
+    N: for<'a> FormatFields<'a> + 'static,
+{
+    fn format_event(
+        &self,
+        ctx: &tracing_subscriber::fmt::FmtContext<'_, S, N>,
+        mut writer: tracing_subscriber::fmt::format::Writer<'_>,
+        event: &tracing::Event<'_>,
+    ) -> fmt::Result {
+        let now = chrono::Local::now();
+        let time = now.format("%H:%M:%S");
+
+        let level = *event.metadata().level();
+        let styled = match level {
+            tracing::Level::ERROR => console::style("ERROR").red().bold(),
+            tracing::Level::WARN => console::style(" WARN").yellow(),
+            tracing::Level::INFO => console::style(" INFO").green(),
+            tracing::Level::DEBUG => console::style("DEBUG").dim(),
+            tracing::Level::TRACE => console::style("TRACE").dim(),
+        };
+
+        write!(writer, "{time} {styled}  ")?;
+        ctx.format_fields(writer.by_ref(), event)?;
+        writeln!(writer)
+    }
+}
 
 pub fn build_stderr_filter(verbose: u8, quiet: bool) -> EnvFilter {
     if std::env::var("RUST_LOG").is_ok() {