[FEATURE]: Discover instructions in ~/.agents

[jasonbcox]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Currently, ~/.agents is only used to discover skills. While a global AGENTS.md is discoverable in ~/.config/opencode this is confusing and non-portable. Why is AGENTS.md loaded from the config when it is not itself a config?

Making AGENTS.md discoverable from ~/.agents fixes the portability issue and fixes a bad code smell:

packages/opencode/src/session/instruction.ts

    const globalFiles = [
      path.join(global.config, "AGENTS.md"),
      ...(!flags.disableClaudeCodePrompt ? [path.join(global.home, ".claude", "CLAUDE.md")] : []),
    ]

With AGENTS.md being an instruction, not a config, it's odd that it's being loaded from global.config