chore(release): regenerate the public API manifest for the Node 20 floor

`scripts/release/public-api/manifest.v1.json` records each published
package's `engines`, so raising the floor left it stale and
`public-api-manifest.test.ts` failed on all six unit shards.

Regenerated with `pnpm generate:public-api-manifest`: seven `>=18`
entries become `>=20`, and `@copilotkit/runtime` gains an `engines`
block with its package-json provenance entry.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/release/public-api/manifest.v1.json

@@ -167,7 +167,7 @@
       ],
       "compatibility": {
         "engines": {
-          "node": ">=18"
+          "node": ">=20"
         },
         "provenance": [
           {
@@ -989,7 +989,7 @@
       ],
       "compatibility": {
         "engines": {
-          "node": ">=18"
+          "node": ">=20"
         },
         "provenance": [
           {
@@ -1587,6 +1587,9 @@
         }
       ],
       "compatibility": {
+        "engines": {
+          "node": ">=20"
+        },
         "peerDependencies": {
           "@anthropic-ai/sdk": ">=0.57.0",
           "@langchain/aws": ">=0.1.9",
@@ -1611,6 +1614,11 @@
           "openai"
         ],
         "provenance": [
+          {
+            "kind": "package-json",
+            "path": "packages/runtime/package.json",
+            "selector": "engines"
+          },
           {
             "kind": "package-json",
             "path": "packages/runtime/package.json",
@@ -1917,7 +1925,7 @@
       ],
       "compatibility": {
         "engines": {
-          "node": ">=18"
+          "node": ">=20"
         },
         "peerDependencies": {
           "better-sqlite3": "^12.2.0"
@@ -1994,7 +2002,7 @@
       ],
       "compatibility": {
         "engines": {
-          "node": ">=18"
+          "node": ">=20"
         },
         "peerDependencies": {
           "@copilotkit/runtime": "workspace:*"
@@ -2100,7 +2108,7 @@
       ],
       "compatibility": {
         "engines": {
-          "node": ">=18"
+          "node": ">=20"
         },
         "peerDependencies": {
           "vue": ">=3.3.0"
@@ -2195,7 +2203,7 @@
       ],
       "compatibility": {
         "engines": {
-          "node": ">=18"
+          "node": ">=20"
         },
         "peerDependencies": {
           "lit": "^3.3.2"
@@ -2264,7 +2272,7 @@
       ],
       "compatibility": {
         "engines": {
-          "node": ">=18"
+          "node": ">=20"
         },
         "provenance": [
           {