Add OpenCode Extension (/skillspector + Tool) #535

As an OpenCode user, I want a native /skillspector slash command and skillspector_scan agent tool so I can scan skills directly from my OpenCode session without manual CLI invocation.

The gap

OpenCode users have no native way to invoke SkillSpector: no slash command, no agent-callable tool, so scans require manual CLI use outside the session.

What I am asking for

Please consider shipping OpenCode-native invocation support: a /skillspector slash command plus a skillspector_scan agent tool, both auto-discovered through OpenCode's file-based tools/commands directories with zero new dependencies. Done when an OpenCode user can type /skillspector <target> (or have the agent call the tool) and get back a static-analysis report by default, with LLM semantic analysis strictly opt-in — including clean behavior for missing binaries, timeouts, and usage errors.

This could be achieved by

• Creating .opencode/tools/skillspector_scan.ts — tool wrapping skillspector CLI via execFile with binary chain (env → venv → PATH), 120s timeout, output truncation, secret redaction
• Creating .opencode/commands/skillspector.md — slash command forwarding $ARGUMENTS with LLM opt-in
• Defaulting to --no-llm for instant static scans; LLM opt-in via noLlm=false or env passthrough
• Headless load test confirms auto-discovery, JSON flow, exit-code semantics (0=success, 1=findings, 2=usage error)