Add machine-readable --json flag to query and inspection commands

[jon-devlapaz]

Problem

Tink CLI commands such as tink inspect <URL>, tink skill list, tink skillset list, and tink library list output human-targeted text or TSV tables.

For AI agents and automated tooling, parsing unstructured or tabular CLI output is brittle:

• Parsing tink inspect requires regex or indentation scraping to extract candidates, SHAs, and member paths.
• TSV tables require splitting and escaping handling.
• Any change to human CLI formatting risks breaking agent workflows.

Proposed change

Add a --json flag to read and query operations:

• tink inspect <URL> --json: outputs structured JSON containing repository URL, boundary, resolved commit SHA, standalone skills, and skillset candidates with member lists.
• tink skill list --json: outputs installed skills, versions, and paths.
• tink skillset list [--library] --json: outputs installed/library skillsets, members, and status.
• tink library list --json: outputs available library skills and provenance.

Acceptance

• --json flag emits valid, deterministic JSON on stdout.
• Errors during JSON execution emit structured JSON error objects on stderr/stdout when --json is active.
• Output schema covers all fields rendered in human-readable output.