feat: TOON re-encoder for JSON-array outputs (gh, kubectl, aws, gcloud, az) #128

Problem

Many cloud-CLI invocations return a top-level JSON array of uniform flat objects: gh pr list --json …, kubectl get pods -o json, aws ec2 describe-instances --output json, gcloud compute instances list --format=json. JSON repeats every field name on every row. Today CloudHandler only strips noise; the heavy redundant field repetition stays in context.

Token-Oriented Object Notation (TOON, https://github.com/toon-format/toon) is a schema-aware JSON replacement that declares the schema once in a header and lists rows CSV-style. Independent benchmarks report ~40% fewer tokens on this exact shape — typically more.

Concrete example, raw gh pr list --json number,title,state:

[
    {"number": 1, "title": "Add feature", "state": "OPEN"},
    {"number": 2, "title": "Fix bug", "state": "MERGED"}
]

TOON:

items[2]{number,title,state}:
  1,Add feature,OPEN
  2,Fix bug,MERGED

Proposal

New src/strategies/toon.rs with:

• pub fn try_to_toon(text: &str) -> Option<String> — zero-dep hand-rolled JSON sub-parser + TOON emitter.
• Strictly lossless-or-reject: returns None for any non-uniform / nested / out-of-order / unsmaller input.
• CloudHandler calls it when the command requests JSON (--json, -o json, -ojson, --output json, --output=json, --format json, --format=json, -f json); otherwise pipes through to the existing pipeline unchanged.

Tradeoff

• Slightly more code on the cloud handler path (~340 LoC including tests).
• Zero new runtime deps.
• Never makes a scenario worse: if the TOON output isn't smaller than the input, we return None and fall back.

Out of scope

• NDJSON streams from docker ps --format '{{json .}}' — follow-up.
• cargo metadata --format-version 1 — nested by design, not worth TOON.

Area

• Handler (src/commands/*)
• Compression pipeline (src/strategies/)

Confirmations

• I've searched existing issues and this isn't a duplicate.
• This respects the zero-runtime-dependency rule (only libc allowed in Cargo.toml).