fix(core): warn when focus depth is clamped to MAX_FOCUS_DEPTH

Previously, FocusSpec silently clamped depth values exceeding
MAX_FOCUS_DEPTH (10).  Now emit a tracing::warn with the requested
and maximum values so users are aware their input was adjusted.

Author: mhiro2

Cargo.lock

@@ -10,6 +10,7 @@ petgraph.workspace = true
 serde.workspace = true
 serde_json = { workspace = true }
 thiserror.workspace = true
+tracing.workspace = true
 
 [lints]
 workspace = true

crates/relune-core/Cargo.toml

@@ -33,13 +33,27 @@ where
     D: serde::Deserializer<'de>,
 {
     let value = u32::deserialize(deserializer)?;
+    if value > MAX_FOCUS_DEPTH {
+        tracing::warn!(
+            requested = value,
+            max = MAX_FOCUS_DEPTH,
+            "focus depth exceeds maximum, clamping to {MAX_FOCUS_DEPTH}",
+        );
+    }
     Ok(value.min(MAX_FOCUS_DEPTH))
 }
 
 impl FocusSpec {
     /// Creates a new `FocusSpec`, clamping `depth` to [`MAX_FOCUS_DEPTH`].
     #[must_use]
     pub fn new(table: impl Into<String>, depth: u32) -> Self {
+        if depth > MAX_FOCUS_DEPTH {
+            tracing::warn!(
+                requested = depth,
+                max = MAX_FOCUS_DEPTH,
+                "focus depth exceeds maximum, clamping to {MAX_FOCUS_DEPTH}",
+            );
+        }
         Self {
             table: table.into(),
             depth: depth.min(MAX_FOCUS_DEPTH),