[Audit] Add --json output to 28 commands for CI/CD usage

[rohitg00]

Problem

28 commands lack --json structured output, making them hard to use in CI/CD pipelines:

install, translate, scan, sync, publish, remove, find, init, check, cicd, create, enable, eval, fix, manifest, methodology, pause, plugin, read, resume, save, serve, team, ui, update, agents-md, quick

Why This Matters

• CI/CD pipelines need parseable output to make decisions
• skillkit install --json should return { skills: [...], agents: [...], success: true }
• skillkit scan --json should return structured findings for security gates
• skillkit sync --json should report what changed

Proposed Solution

Add --json flag (Boolean option) to each command. When set:

1. Suppress interactive prompts (imply --yes)
2. Suppress colored/styled output
3. Output a single JSON object to stdout
4. Exit with non-zero code on failure

Priority

Start with the most CI/CD-relevant commands:

1. install, sync, scan, translate, publish, remove
2. Then find, check, update, validate
3. Then the rest

Acceptance Criteria

• All commands accept --json flag
• JSON output is valid, parseable, and documented
• Non-interactive mode works with --json in CI