refactor(ui): extract ChoosePathButton into reusable PathInstructionsModal

Move the directory picker button and instructions modal out of
AgentConfigForm into its own component, reused by claude-local and
codex-local config fields.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/adapters/codex-local/config-fields.tsx

@@ -5,6 +5,7 @@ import {
   DraftInput,
   help,
 } from "../../components/agent-config-primitives";
+import { ChoosePathButton } from "../../components/PathInstructionsModal";
 
 const inputClass =
   "w-full rounded-md border border-border px-2.5 py-1.5 bg-transparent outline-none text-sm font-mono placeholder:text-muted-foreground/40";
@@ -25,25 +26,28 @@ export function CodexLocalConfigFields({
   return (
     <>
       <Field label="Agent instructions file" hint={instructionsFileHint}>
-        <DraftInput
-          value={
-            isCreate
-              ? values!.instructionsFilePath ?? ""
-              : eff(
-                  "adapterConfig",
-                  "instructionsFilePath",
-                  String(config.instructionsFilePath ?? ""),
-                )
-          }
-          onCommit={(v) =>
-            isCreate
-              ? set!({ instructionsFilePath: v })
-              : mark("adapterConfig", "instructionsFilePath", v || undefined)
-          }
-          immediate
-          className={inputClass}
-          placeholder="/absolute/path/to/AGENTS.md"
-        />
+        <div className="flex items-center gap-2">
+          <DraftInput
+            value={
+              isCreate
+                ? values!.instructionsFilePath ?? ""
+                : eff(
+                    "adapterConfig",
+                    "instructionsFilePath",
+                    String(config.instructionsFilePath ?? ""),
+                  )
+            }
+            onCommit={(v) =>
+              isCreate
+                ? set!({ instructionsFilePath: v })
+                : mark("adapterConfig", "instructionsFilePath", v || undefined)
+            }
+            immediate
+            className={inputClass}
+            placeholder="/absolute/path/to/AGENTS.md"
+          />
+          <ChoosePathButton />
+        </div>
       </Field>
       <ToggleField
         label="Bypass sandbox"