fix(lsp-gate): lint-tagged diagnostics never fail a stage (#311)

tsserver tags TS6133 (unused import) Unnecessary, but a tsconfig with
noUnusedLocals promotes it to error severity — which hard-failed whole
runs no rewrite could clear. Carry LSP DiagnosticTag through the
LspDiagnostic event and gate on untagged errors only; lint diagnostics
stay recorded and visible.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

core/kernel/src/main/kotlin/com/correx/core/kernel/orchestration/SessionOrchestratorGates2.kt

@@ -97,7 +97,9 @@ internal suspend fun SessionOrchestrator.runLspDiagnostics(
         sessionId,
         LspDiagnosticsCompletedEvent(sessionId, stageId, result.server, diagnostics, result.skippedReason),
     )
-    val errors = diagnostics.filter { it.severity.equals("error", ignoreCase = true) }
+    // Lint-class diagnostics (unused import, deprecated) are recorded above but never gate: a
+    // tsconfig with noUnusedLocals promotes them to "error" severity, which no rewrite can clear.
+    val errors = diagnostics.filter { it.severity.equals("error", ignoreCase = true) && !it.isLint }
     if (errors.isEmpty()) return StageExecutionResult.Success(emptyList())
     val detail = errors.joinToString("\n") {
         "- ${it.path}:${it.line + 1}:${it.character + 1} ${it.code.orEmpty()} ${it.message}".trim()