fix: single config flag for skill discovery, default false (opt-in)

Remove env var gate (OPENCODE_DISABLE_EXTERNAL_SKILLS) — only the
config flag controls discovery. Default changed from true to false
so users must explicitly opt in with auto_skill_discovery: true.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: kulvirgit

packages/opencode/src/config/config.ts

@@ -1303,8 +1303,8 @@ export namespace Config {
           // altimate_change start - auto skill/command discovery toggle
           auto_skill_discovery: z
             .boolean()
-            .default(true)
-            .describe("Auto-discover skills and commands from Claude Code, Codex, and Gemini configs at startup. Set to false to disable."),
+            .default(false)
+            .describe("Auto-discover skills and commands from Claude Code, Codex, and Gemini configs at startup. Opt-in — set to true to enable."),
           // altimate_change end
         })
         .optional(),

packages/opencode/src/skill/skill.ts

@@ -231,7 +231,7 @@ export namespace Skill {
     }
 
     // altimate_change start — auto-discover skills/commands from external AI tool configs
-    if (!Flag.OPENCODE_DISABLE_EXTERNAL_SKILLS && config.experimental?.auto_skill_discovery !== false) {
+    if (config.experimental?.auto_skill_discovery === true) {
       try {
         const { discoverExternalSkills, setSkillDiscoveryResult } = await import("./discover-external")
         const { skills: externalSkills, sources } = await discoverExternalSkills(Instance.worktree)