feat(agent): auto-discover workspace .claude skills/agents/commands + /plan alias

[Besthope-Official]

Use Case

Teams keep reusable automation in .claude/skills, .claude/agents, and .claude/commands, but Codex does not ingest these by default.
This forces manual duplication into AGENTS.md, causes drift, and makes /plan workflows non-portable across Claude Code and Codex.

Proposed Solution

Add an opt-in Claude-compatibility layer in Codex CLI:

• Add config flag: features.claude_compat = true in codex.toml.
• On session start, scan workspace-local:
  • .claude/skills/**/SKILL.md
  • .claude/agents/**/*.md
  • .claude/commands/**/*.md
• Register discovered entries in Codex runtime as first-class skills/agents/commands.
• Support command alias mapping so .claude/commands/plan.md can invoke Codex plan workflow (/plan).
• Enforce precedence: system/developer instructions > AGENTS.md > .claude/*.

Alternatives Considered

• Manual mirroring from .claude/* into AGENTS.md (high maintenance, drift risk).
• External conversion script per repo (extra tooling burden, inconsistent behavior).
• Keep current behavior (no compatibility) and require explicit prompts each session.

Implementation Notes

• Discovery must be workspace-scoped only (no parent directory traversal).
• Loaded .claude entries must remain instruction-only unless normal tool permissions allow execution.
• Feature must be disabled by default.
• Reuse existing single-source sync pattern already used in templates (AGENTS.md -> other agent files via scripts/agent_rules.py + CI check), so Claude-compat discovery does not create a second unsynced source of truth.
• If a better model is introduced, prefer one canonical machine-readable manifest (agent-neutral) and generate .claude/* + AGENTS.md views from it in CI.
• Acceptance criteria:
  • New session auto-lists .claude skills/agents/commands when enabled.
  • Referencing discovered skill/agent uses normal loading behavior.
  • /plan alias works via mapped command template when enabled.
  • No change in behavior when features.claude_compat is absent or false.