fix(config): remove instructionsFilePath from UI config schema

Handled by the framework via instructionsPathKey/supportsInstructionsBundle.
Surfacing it as an editable field in the config schema was redundant.

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

src/server/config-schema.ts

@@ -11,13 +11,6 @@ export function getConfigSchema(): AdapterConfigSchema {
         hint: "Provider-specific reasoning/profile variant passed as --variant",
         group: "Core",
       },
-      {
-        key: "instructionsFilePath",
-        label: "Instructions File Path",
-        type: "text",
-        hint: "Absolute path to a markdown file (e.g. AGENTS.md) prepended as system instructions before the task prompt",
-        group: "Core",
-      },
       {
         key: "dangerouslySkipPermissions",
         label: "Skip Permission Checks",