docs: document JSON log format toggle

docs/setup-robusta/index.rst

@@ -16,6 +16,7 @@
    multi-cluster
    upgrade
    tuning-performance
+   json-logging
    configuration-secrets
    openshift
    read-only-service-account

docs/setup-robusta/json-logging.rst

@@ -0,0 +1,28 @@
+JSON Log Format
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+By default, Robusta components emit human-readable, colored text logs. You can
+switch them to **structured JSON logs** (one JSON object per line), which are
+easier to index, search, and filter with log collectors such as Filebeat,
+Fluent Bit, or Loki.
+
+Enabling JSON Logs
+-------------------------------------
+
+Set the ``global.enableJsonLogsFormat`` value in your Helm values:
+
+.. code-block:: yaml
+
+    global:
+      enableJsonLogsFormat: true
+
+This single switch is shared across the Robusta components:
+
+* **robusta-runner** emits JSON logs.
+* **KRR** scan jobs inherit the setting from the runner (when scan results are
+  pushed back over the API, which is the default).
+* **HolmesGPT** (when deployed via the chart) emits JSON logs as well — the
+  ``global`` value is passed through to the Holmes sub-chart.
+
+The default is ``false``, which preserves the existing colored text output. No
+change is needed unless you want JSON logs.