refactor: move delay from mock to query/mutation level

Move the `delay` field from mock configuration to the query/mutation
top level, allowing delay to be used with both SQL and mock sources.

Changes:
- Remove Delay from config.Mock struct
- Add Delay to config.Query and config.Mutation structs
- Update handler to parse and apply delay before response
- Remove internal/mock/delay.go (no longer needed)
- Update schema.json, SCHEMA.md, and example config
- Rename e2e/mock_delay_test.* to e2e/delay_test.*

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: mpyw

SCHEMA.md

@@ -24,8 +24,8 @@ This document describes all configuration options for sql-http-proxy. For usage
     - [Object Sources](#object-sources-type-one-only)
     - [Array Sources](#array-sources-type-many-or-type-one-with-filter)
   - [Filter](#filter)
-  - [Delay](#delay)
   - [Mock JS Variables](#mock-js-variables)
+- [Delay](#delay)
 - [Transform](#transform)
   - [Pre-Transform](#pre-transform)
   - [Post-Transform](#post-transform)
@@ -415,14 +415,16 @@ The `filter` option allows filtering array data using JavaScript.
     filter: return row.role === input.role
 ```
 
-### Delay
+## Delay
 
-Add artificial latency to mock responses. Useful for testing loading states and timeouts.
+Add artificial latency to responses. Useful for testing loading states and timeouts.
 
 ```yaml
-mock:
-  object: { id: 1, name: Alice }
-  delay: 500ms
+queries:
+  - type: one
+    path: /slow-user
+    delay: 500ms
+    sql: SELECT * FROM users WHERE id = :id
 ```
 
 | Value | Description |
@@ -432,20 +434,23 @@ mock:
 **Supported units:** `ns`, `us`/`µs`, `ms`, `s`, `m`, `h`
 
 ```yaml
-# With array source
-mock:
-  array:
-    - { id: 1, name: Alice }
-    - { id: 2, name: Bob }
-  delay: 1s
-
-# With filter
-mock:
-  array:
-    - { id: 1, name: Alice }
-    - { id: 2, name: Bob }
-  filter: return row.id == parseInt(input.id)
-  delay: 200ms
+# With mock source
+queries:
+  - type: many
+    path: /slow-users
+    delay: 1s
+    mock:
+      array:
+        - { id: 1, name: Alice }
+        - { id: 2, name: Bob }
+
+# With mutations
+mutations:
+  - type: one
+    method: POST
+    path: /slow-create
+    delay: 200ms
+    sql: INSERT INTO users (name) VALUES (:name) RETURNING *
 ```
 
 ### Mock JS Variables

e2e/mock_delay_test.go e2e/delay_test.goe2e/mock_delay_test.go renamed to e2e/delay_test.go

@@ -12,8 +12,8 @@ import (
 	"github.com/mpyw/sql-http-proxy/internal/server"
 )
 
-func TestMockDelay(t *testing.T) {
-	cfg, err := config.ParseFile("mock_delay_test.yaml")
+func TestDelay(t *testing.T) {
+	cfg, err := config.ParseFile("delay_test.yaml")
 	require.NoError(t, err)
 
 	mux, err := server.NewServeMux(nil, cfg, ".")

e2e/mock_delay_test.yaml e2e/delay_test.yamle2e/mock_delay_test.yaml renamed to e2e/delay_test.yaml

@@ -2,38 +2,38 @@ queries:
   # Object source with delay
   - type: one
     path: /slow-user
+    delay: 50ms
     mock:
       object:
         id: 1
         name: Slow User
-      delay: 50ms
 
   # Array source with delay
   - type: many
     path: /slow-users
+    delay: 50ms
     mock:
       array:
         - { id: 1, name: Alice }
         - { id: 2, name: Bob }
-      delay: 50ms
 
   # Array source with filter and delay
   - type: one
     path: /slow-filtered-user
+    delay: 50ms
     mock:
       array:
         - { id: 1, name: Alice }
         - { id: 2, name: Bob }
       filter: return row.id == parseInt(input.id)
-      delay: 50ms
 
   # JS source with delay
   - type: one
     path: /slow-js-user
+    delay: 50ms
     mock:
       object_js: |
         return { id: parseInt(input.id), name: "JS User" };
-      delay: 50ms
 
   # Zero delay (no actual delay)
   - type: one