fix: quiet noisy store poll and skill-resolver info logs

Raise checkForChanges slow-poll warn threshold from 100ms to 750ms so
warnings only fire when cycles approach the 1s poll interval, and route
skill-resolver info diagnostics through log() instead of warn().

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/engine/src/skill-resolver.ts

@@ -471,7 +471,10 @@ export function createSkillsOverrideFromSelection(
     if (newDiagnostics.length > 0) {
       const _purpose = sessionPurpose ? `[${sessionPurpose}]` : "skills";
       for (const diag of newDiagnostics) {
-        piLog.warn(`[skills] ${diag.type}: ${diag.message}`);
+        const msg = `[skills] ${diag.type}: ${diag.message}`;
+        if (diag.type === "error") piLog.error(msg);
+        else if (diag.type === "warning") piLog.warn(msg);
+        else piLog.log(msg);
       }
     }