core: modularize config parsing to improve maintainability

Extract error handling, parsing logic, and variable substitution into dedicated
modules. This reduces duplication between tui.json and opencode.json parsing
and makes the config system easier to extend for future config formats.

packages/opencode/src/cli/cmd/tui/config/tui.ts

@@ -1,6 +1,7 @@
 import z from "zod"
 import { mergeDeep, unique } from "remeda"
 import { Context, Effect, Fiber, Layer } from "effect"
+import { ConfigParse } from "@/config/parse"
 import * as ConfigPaths from "@/config/paths"
 import { migrateTuiConfig } from "./tui-migrate"
 import { TuiInfo } from "./tui-schema"
@@ -68,6 +69,14 @@ export namespace TuiConfig {
     }
   }
 
+  async function resolvePlugins(config: Info, configFilepath: string) {
+    if (!config.plugin) return config
+    for (let i = 0; i < config.plugin.length; i++) {
+      config.plugin[i] = await ConfigPlugin.resolvePluginSpec(config.plugin[i], configFilepath)
+    }
+    return config
+  }
+
   async function mergeFile(acc: Acc, file: string, ctx: { directory: string }) {
     const data = await loadFile(file)
     acc.result = mergeDeep(acc.result, data)
@@ -183,26 +192,22 @@ export namespace TuiConfig {
   }
 
   async function load(text: string, configFilepath: string): Promise<Info> {
-    const raw = await ConfigPaths.parseText(text, configFilepath, "empty")
-    if (!isRecord(raw)) return {}
+    return ConfigParse.load(Info, text, {
+      type: "path",
+      path: configFilepath,
+      missing: "empty",
+      normalize: (data) => {
+        if (!isRecord(data)) return {}
 
-    // Flatten a nested "tui" key so users who wrote `{ "tui": { ... } }` inside tui.json
-    // (mirroring the old opencode.json shape) still get their settings applied.
-    const normalized = normalize(raw)
-
-    const parsed = Info.safeParse(normalized)
-    if (!parsed.success) {
-      log.warn("invalid tui config", { path: configFilepath, issues: parsed.error.issues })
-      return {}
-    }
-
-    const data = parsed.data
-    if (data.plugin) {
-      for (let i = 0; i < data.plugin.length; i++) {
-        data.plugin[i] = await ConfigPlugin.resolvePluginSpec(data.plugin[i], configFilepath)
-      }
-    }
-
-    return data
+        // Flatten a nested "tui" key so users who wrote `{ "tui": { ... } }` inside tui.json
+        // (mirroring the old opencode.json shape) still get their settings applied.
+        return normalize(data)
+      },
+    })
+      .then((data) => resolvePlugins(data, configFilepath))
+      .catch((error) => {
+        log.warn("invalid tui config", { path: configFilepath, error })
+        return {}
+      })
   }
 }