[Feature] Add local/project-scoped installation support

[Pablo-Lozano-Gil]

📋 Pre-flight Checks

• I have searched existing issues and this is not a duplicate
• I understand this issue needs status:approved before a PR can be opened

🔍 Problem Description

Agent Teams Lite currently only supports global installation, with hardcoded paths in:

• OpenCode commands (~/.config/opencode/skills/sdd-*/SKILL.md)
• Agent prompts (opencode.json references global paths)
• setup.sh only installs to global directories
  This creates several problems for team collaboration:

1. Global environment pollution – skills and configuration affect all projects
2. No project-specific customization – cannot have different SDD conventions per project
3. Team synchronization issues – each developer must manually install/update globally
4. Hardcoded paths prevent local discovery – OpenCode already supports local skill discovery but agent-teams-lite doesn't use it

💡 Proposed Solution

Add a --local (or --project) flag to setup.sh that enables project-scoped installation:
Phase 1: Local installation mode

• ./setup.sh --local detects git repo and installs to project directories
• Skills go to ./.opencode/skills/, ./.claude/skills/, etc.
• Configuration merges into ./.opencode/opencode.json, ./.claude/CLAUDE.md
• Commands copy to ./.opencode/commands/ (without hardcoded paths)
  Phase 2: Path-agnostic prompts
• Remove hardcoded ~/.config/opencode/skills/... references from commands and agent prompts
• Rely on OpenCode's built-in skill discovery (local > global hierarchy)
• Use skill({name: "sdd-apply"}) instead of explicit file paths
  Phase 3: Example project template
• Add examples/local-project/ showing the ideal structure
• Include documentation for team setup

📦 Affected Area

Scripts (setup, installation)

🔄 Alternatives Considered

1. Symlinks from global to local – still pollutes global namespace, requires per-user setup
2. Environment variables to override paths – complex, breaks agent discovery patterns
3. Manual copy-paste of skills – error-prone, not maintainable

📎 Additional Context

• Related to issue [Feature] Support per-project local configuration instead of global #16 (similar request but without template/status)
• OpenCode documentation confirms local skill discovery is already supported
• Many teams need consistent SDD workflows across repositories without global side effects