fix(query-enhancements): nest PPL lint flag under ppl.lint.enabled

Address joshuali925's review on #12255: restructure the config path from
queryEnhancements.pplLint.enabled to queryEnhancements.ppl.lint.enabled so
future languages/features (ppl.autocomplete, sql.lint) extend the same
shape. The wire capability stays a flat boolean queryEnhancements.pplLint,
so capability consumers are unaffected; only the DynamicConfigService read
in the switcher changes (config.ppl?.lint?.enabled === true).

Signed-off-by: Hanyu Wei <weihanyu@amazon.com>

Author: Hanyu Wei

src/plugins/query_enhancements/common/config.ts

@@ -31,10 +31,14 @@ export const configSchema = schema.object({
       }),
     }),
   }),
-  // PPL linter feature flag, read at runtime via DynamicConfigService and
-  // surfaced as the queryEnhancements.pplLint capability. Disabled by default.
-  pplLint: schema.object({
-    enabled: schema.boolean({ defaultValue: false }),
+  // PPL feature flags, read at runtime via DynamicConfigService. Nested as
+  // ppl.lint.enabled so future languages/features (ppl.autocomplete, sql.lint)
+  // extend the same shape. Surfaced as the flat queryEnhancements.pplLint
+  // capability. Disabled by default.
+  ppl: schema.object({
+    lint: schema.object({
+      enabled: schema.boolean({ defaultValue: false }),
+    }),
   }),
 });
 

src/plugins/query_enhancements/server/plugin.test.ts

@@ -62,7 +62,7 @@ describe('QueryEnhancementsPlugin pplLint capability', () => {
 
   it('enables pplLint when the dynamic config flag is on', async () => {
     const { core, switcher } = setupPlugin();
-    const startContract = stubConfig(core, { pplLint: { enabled: true } });
+    const startContract = stubConfig(core, { ppl: { lint: { enabled: true } } });
 
     const result = await switcher({} as any, baseCapabilities());
 
@@ -80,7 +80,7 @@ describe('QueryEnhancementsPlugin pplLint capability', () => {
   it('passes the async local store as context when one is present', async () => {
     const { core, switcher } = setupPlugin();
     const store = new Map<string, any>([['k', 'v']]);
-    const startContract = stubConfig(core, { pplLint: { enabled: true } }, store);
+    const startContract = stubConfig(core, { ppl: { lint: { enabled: true } } }, store);
 
     await switcher({} as any, baseCapabilities());
 
@@ -92,7 +92,7 @@ describe('QueryEnhancementsPlugin pplLint capability', () => {
     const { core, switcher } = setupPlugin();
     // No store passed → getAsyncLocalStore() returns undefined. The switcher
     // must pass `undefined` rather than { asyncLocalStorageContext: undefined }.
-    const startContract = stubConfig(core, { pplLint: { enabled: true } });
+    const startContract = stubConfig(core, { ppl: { lint: { enabled: true } } });
 
     await switcher({} as any, baseCapabilities());
 
@@ -104,7 +104,7 @@ describe('QueryEnhancementsPlugin pplLint capability', () => {
     const { core, switcher } = setupPlugin();
     // Dynamic config writes are not schema-validated, so the store can hold a
     // string. Only a real boolean `true` may enable the flag.
-    stubConfig(core, { pplLint: { enabled: 'true' } } as any);
+    stubConfig(core, { ppl: { lint: { enabled: 'true' } } } as any);
 
     const result = await switcher({} as any, baseCapabilities());
 
@@ -113,7 +113,7 @@ describe('QueryEnhancementsPlugin pplLint capability', () => {
 
   it('leaves pplLint off when the dynamic config flag is false', async () => {
     const { core, switcher } = setupPlugin();
-    stubConfig(core, { pplLint: { enabled: false } });
+    stubConfig(core, { ppl: { lint: { enabled: false } } });
 
     const result = await switcher({} as any, baseCapabilities());
 

src/plugins/query_enhancements/server/plugin.ts

@@ -84,7 +84,7 @@ export class QueryEnhancementsPlugin
         return {
           queryEnhancements: {
             ...(capabilities.queryEnhancements || {}),
-            pplLint: config.pplLint?.enabled === true,
+            pplLint: config.ppl?.lint?.enabled === true,
           },
         };
       } catch (error) {