fix(cli): close small JSON-contract gaps for agent consumers

- --offline now warns when it serves a cache entry past its TTL; before,
  arbitrarily old data was returned with no signal at all
- version, cache info and cache clear honour -o json
- ownership resolve map/merge honour -o json
- stocks quote/compare require at least one symbol instead of printing []
- cache schema-mismatch notice goes through runtime::info so --quiet
  silences it, instead of a raw debug eprintln

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013Q2PufCUdvVZoVW1Dy53js

src/cache.rs

@@ -52,11 +52,7 @@ impl Cache {
         let Some(entry): Option<CacheEntry<T>> = self.read_entry(data_type, symbol)? else {
             return Ok(None);
         };
-        let age = Utc::now().signed_duration_since(entry.fetched_at);
-        if age
-            >= chrono::Duration::from_std(Duration::from_secs(entry.ttl_secs))
-                .map_err(|e| IdxError::CacheMiss(e.to_string()))?
-        {
+        if is_expired(entry.fetched_at, entry.ttl_secs) {
             return Ok(None);
         }
         Ok(Some(entry.data))
@@ -70,6 +66,25 @@ impl Cache {
         Ok(self.read_entry::<T>(data_type, symbol)?.map(|e| e.data))
     }
 
+    /// Like [`Cache::get_stale`], but warns when the entry served is past its TTL.
+    /// Used by `--offline`, which otherwise serves arbitrarily old data silently.
+    pub fn get_offline<T: DeserializeOwned>(
+        &self,
+        data_type: &str,
+        symbol: &str,
+    ) -> Result<Option<T>, IdxError> {
+        let Some(entry) = self.read_entry::<T>(data_type, symbol)? else {
+            return Ok(None);
+        };
+        if is_expired(entry.fetched_at, entry.ttl_secs) {
+            runtime::warn(format!(
+                "offline: serving expired cache for {symbol} (fetched {})",
+                entry.fetched_at.to_rfc3339()
+            ));
+        }
+        Ok(Some(entry.data))
+    }
+
     pub fn put<T: Serialize>(
         &self,
         data_type: &str,
@@ -184,12 +199,12 @@ impl Cache {
             }
         };
         if entry.schema_version != CURRENT_SCHEMA_VERSION {
-            eprintln!(
-                "debug: cache schema mismatch for {} (got {}, expected {})",
+            runtime::info(format!(
+                "cache schema mismatch for {} (got {}, expected {}), treating as miss",
                 path.display(),
                 entry.schema_version,
                 CURRENT_SCHEMA_VERSION
-            );
+            ));
             let _ = fs::remove_file(&path);
             return Ok(None);
         }
@@ -201,6 +216,12 @@ impl Cache {
     }
 }
 
+fn is_expired(fetched_at: DateTime<Utc>, ttl_secs: u64) -> bool {
+    let ttl =
+        chrono::Duration::from_std(Duration::from_secs(ttl_secs)).unwrap_or(chrono::Duration::MAX);
+    Utc::now().signed_duration_since(fetched_at) >= ttl
+}
+
 pub fn cache_dir() -> Result<PathBuf, IdxError> {
     if let Ok(dir) = std::env::var("XDG_CACHE_HOME")
         && !dir.is_empty()