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/events/src/main/kotlin/com/correx/core/events/events/LspDiagnosticEvents.kt

@@ -13,7 +13,12 @@ data class LspDiagnostic(
     val severity: String,
     val code: String? = null,
     val message: String,
-)
+    /** LSP `DiagnosticTag` names, lowercased ("unnecessary", "deprecated"). Lint class, not severity. */
+    val tags: List<String> = emptyList(),
+) {
+    /** Lint-class diagnostic: reported and recorded, but never a reason to fail a stage. */
+    val isLint: Boolean get() = tags.isNotEmpty()
+}
 
 /** Recorded LSP 3.17 pull-diagnostic observation; replay never re-queries a language server. */
 @Serializable

core/events/src/test/kotlin/com/correx/core/events/events/LspDiagnosticTest.kt

@@ -0,0 +1,28 @@
+package com.correx.core.events.events
+
+import kotlin.test.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class LspDiagnosticTest {
+    private fun diagnostic(tags: List<String>) = LspDiagnostic(
+        path = "src/App.tsx",
+        line = 0,
+        character = 0,
+        severity = "error",
+        code = "6133",
+        message = "'React' is declared but its value is never read.",
+        tags = tags,
+    )
+
+    @Test
+    fun `tagged diagnostic is lint class even at error severity`() {
+        assertTrue(diagnostic(listOf("unnecessary")).isLint)
+        assertTrue(diagnostic(listOf("deprecated")).isLint)
+    }
+
+    @Test
+    fun `untagged diagnostic still gates`() {
+        assertFalse(diagnostic(emptyList()).isLint)
+    }
+}

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()