feat(research): enable research tools by default

[tools.research].enabled now defaults true, matching shell/file tools. Safe because
web_fetch is T2 — nothing leaves the machine without operator approval regardless of
the flag; the flag only controls whether the tools are registered. web_search (T1) hits
only the configured SearXNG endpoint.

core/config/src/main/kotlin/com/correx/core/config/CorrexConfig.kt

@@ -140,13 +140,14 @@ data class ToolsConfig(
 }
 
 /**
- * Deep-research workflow (research-workflow-spec). Off by default: enabling it registers the
- * network tools web_search (T1, hits only [searxngUrl]) and web_fetch (T2, operator-approved).
+ * Deep-research workflow (research-workflow-spec). On by default (like shell/file tools):
+ * registers the network tools web_search (T1, hits only [searxngUrl]) and web_fetch (T2, which
+ * is operator-approved, so nothing leaves the machine unapproved regardless of this flag).
  * [searxngUrl] is the self-hosted SearXNG endpoint; [maxFetchBytes] caps a single fetched page.
  */
 @Serializable
 data class ResearchConfig(
-    val enabled: Boolean = false,
+    val enabled: Boolean = true,
     val searxngUrl: String = "http://localhost:8888",
     val maxResults: Int = 8,
     val maxFetchBytes: Long = 10_000_000,