feat: add --toon output format for token-efficient CLI output

[akb4q]

Problem

CLI output currently supports two formats: --json (verbose, high token count) and a human-readable table. For LLM-powered toolchains that consume CLI output programmatically, JSON is wasteful — it duplicates keys on every row and adds structural overhead.

Proposal

Add --toon as a third global output format. TOON (Token-Oriented Object Notation) is a line-oriented, indentation-based data format designed as a compact lossless representation of the JSON data model, optimized for LLM prompt injection.

Design

• Global --toon flag registered in Commander.js
• outputTable: when toonMode is set, prints tabular TOON ([N]{fields}:) instead of cli-table3
• outputJson: when --toon and --json both present, reroutes to outputJsonToon which produces TOON key-value format
• No new runtime dependencies — hand-written formatter (~130 lines in src/lib/output.ts)

Token savings (measured)

projects list on a single project:

• JSON: 989 B / ~250 tokens
• TOON: 129 B / ~32 tokens (7.7× reduction)

Status

Working PR at #215 — this issue tracks the prerequisite checklist before final merge.

• Remove the "needs-issue" label from PR 215
• Final review from @jwfing