fix(core,cli): improve lint output - JSON flag, info/warning counts, severity display (#134)

## Summary

- Respect `--json` flag on all lint exit paths so agents always get machine-readable output
- Separate `infoCount` from `warningCount` in linter results (was conflated)
- Display `info` vs `warning` severity distinctly in lint output

packages/core/src/lint/hyperframeLinter.ts

@@ -737,12 +737,14 @@ export function lintHyperframeHtml(
   }
 
   const errorCount = findings.filter((finding) => finding.severity === "error").length;
-  const warningCount = findings.length - errorCount;
+  const warningCount = findings.filter((finding) => finding.severity === "warning").length;
+  const infoCount = findings.filter((finding) => finding.severity === "info").length;
 
   return {
     ok: errorCount === 0,
     errorCount,
     warningCount,
+    infoCount,
     findings,
   };
 }

packages/core/src/lint/types.ts

@@ -15,6 +15,7 @@ export type HyperframeLintResult = {
   ok: boolean;
   errorCount: number;
   warningCount: number;
+  infoCount: number;
   findings: HyperframeLintFinding[];
 };