news: add opencode entry for new agent and command support

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

modules/misc/news/2025/09/2025-09-16_21-29-29.nix

@@ -0,0 +1,39 @@
+{ config, ... }:
+{
+  time = "2025-09-17T02:29:29+00:00";
+  condition = config.programs.opencode.enable;
+  message = ''
+    The opencode module now supports enhanced customization with custom commands and agents.
+
+    You can now define custom commands and agents for opencode in two ways:
+
+    - Inline content as strings
+    - File paths to external markdown files
+
+    Example configuration:
+
+      programs.opencode = {
+        commands = {
+          # Inline content
+          changelog = '''
+            # Update Changelog Command
+            Update CHANGELOG.md with new entries.
+          ''';
+          # File path
+          fix-issue = ./commands/fix-issue.md;
+        };
+
+        agents = {
+          # Inline content
+          code-reviewer = '''
+            # Code Reviewer Agent
+            Specialized code review assistant.
+          ''';
+          # File path
+          documentation = ./agents/documentation.md;
+        };
+      };
+
+    Commands are stored in ~/.config/opencode/command/ and agents in ~/.config/opencode/agent/.
+  '';
+}