fix(opencode): use json5 parser for trailing comma tolerance (#2023)

* fix(opencode): use json5 parser for trailing comma tolerance

OpenCode CLI writes opencode.json with trailing commas (valid JSONC),
but CC Switch parsed it with serde_json (strict JSON), causing errors
like 'trailing comma at line 35 column 3'.

Switch to json5::from_str which accepts both JSON and JSONC. The json5
crate is already a project dependency. Change error type from
AppError::json() to AppError::Config() since json5::Error differs from
serde_json::Error.

* style(opencode): apply rustfmt to satisfy cargo fmt --check

The previous commit's .map_err(...) chain exceeded rustfmt's default
100-char max_width, breaking CI's `cargo fmt --check`. Let rustfmt
wrap the closure body as a multi-line block. No behavior change.

---------

Co-authored-by: 18067889926 <ming.flute@outlook.com>
Co-authored-by: Jason <farion1231@gmail.com>

src-tauri/src/opencode_config.rs

@@ -61,7 +61,12 @@ pub fn read_opencode_config() -> Result<Value, AppError> {
     }
 
     let content = std::fs::read_to_string(&path).map_err(|e| AppError::io(&path, e))?;
-    serde_json::from_str(&content).map_err(|e| AppError::json(&path, e))
+    json5::from_str(&content).map_err(|e| {
+        AppError::Config(format!(
+            "Failed to parse OpenCode config: {}: {e}",
+            path.display()
+        ))
+    })
 }
 
 pub fn write_opencode_config(config: &Value) -> Result<(), AppError> {