feat: track installed remote skills in boost.json on add-skill

[SagorIslamOfficial]

Issue: #701

This PR adds skill metadata tracking in boost.json for skills installed through boost:add-skill. Skills are now stored as a map keyed by skill name, which keeps the config backward compatible while leaving room for per-skill metadata such as source type, GitHub repo, and nested path.

Example

"skills": {
    "laravel-best-practices": {
        "source": "official"
    },
    "my-local-skill": {
        "source": "custom"
    },
    "react-best-practices": {
        "source": "github",
        "repo": "SagorIslamOfficial/agent-skills"
    },
    "nested-skill": {
        "source": "github",
        "repo": "owner/repo",
        "path": "path/to/skills/nested-skill"
    }
}

[pushpak1300]

Instead of adding new repositories key can you just not reuse the skills key with different way or maybe deprecate it and arrange in new format also why do we need hash in this case ? we just need the source ? we can just update the skill form source no need to check it right ?

"repositories": {
        "SagorIslamOfficial/agent-skills": {
            "sourceType": "github",
            "skills": {
                "composition-patterns": {
                    "computedHash": "bf90d0a4b83ea054653350f9c67f6de235d3a368"
                },
                "deploy-to-vercel": {
                    "computedHash": "9e25c105ccd1c52691a1e402708bbb216ac78209"
                }
            }
        },
        "anthropics/skills": {
            "sourceType": "github",
            "skills": {
                "algorithmic-art": {
                    "computedHash": "22db2d12091c56340987a877047435ba84a1cdb2"
                }
            }
        }
    }

[SagorIslamOfficial]

Instead of adding new repositories key can you just not reuse the skills key with different way or maybe deprecate it and arrange in new format also why do we need hash in this case ? we just need the source ? we can just update the skill form source no need to check it right ?

"repositories": {
        "SagorIslamOfficial/agent-skills": {
            "sourceType": "github",
            "skills": {
                "composition-patterns": {
                    "computedHash": "bf90d0a4b83ea054653350f9c67f6de235d3a368"
                },
                "deploy-to-vercel": {
                    "computedHash": "9e25c105ccd1c52691a1e402708bbb216ac78209"
                }
            }
        },
        "anthropics/skills": {
            "sourceType": "github",
            "skills": {
                "algorithmic-art": {
                    "computedHash": "22db2d12091c56340987a877047435ba84a1cdb2"
                }
            }
        }
    }

Hi, I’ve made the updates based on your instructions. When you have a moment, please review and let me know if there’s anything else I can do.

[SagorIslamOfficial]

@pushpak1300 Hi, it's been a while since this PR was reviewed. Is there anything I can do to help?