fix(jsonfmt): expand non-empty arrays

[sidsri14]

Summary

• expand non-empty root and property arrays to one element per line in JSON and JSONC
• keep empty arrays and short nested array elements compact
• remove the obsolete numeric fill layout and update canonical fixtures

Fixes #630

Testing

• go test -count=1 -cover -coverprofile=/tmp/cfv-coverage.out ./... (92.3% total coverage)
• golangci-lint v2.11.4 run ./... (0 issues)
• go vet ./...
• gofmt -s -l -e .
• go generate ./pkg/filetype/... with a clean generated-file diff
• CI-equivalent static Linux build

[kehoecj]

Thanks for working on this @sidsri14! The code is clean and your isInlineArrayElement / inlineArrayValueLength changes work as intended.

When I was running this through the parity test suite, I realized I messed up the issue description. I said "always expand non-empty arrays" but that isn't actually what prettier does. I went and read prettier's source (src/language-js/print/array.js) and here's the real rule:

Short arrays stay on one line when they fit:

Input:  {"items": ["a", "b", "c"]}
prettier: { "items": ["a", "b", "c"] }
This PR: { "items": [\n    "a",\n    "b",\n    "c"\n  ] }

So given that, we need to keep the current collapse behavior here.

Arrays where every element is an array/object force-expand:

Input:  {"brackets": [["{","}"],["[","]"],["(",")"]]}
prettier:
{
  "brackets": [
    ["{", "}"],
    ["[", "]"],
    ["(", ")"]
  ]
}
Current cfv: "brackets": [["{", "}"], ["[", "]"], ["(", ")"]]

This is what needs to change: cfv collapses these when prettier expands them.

The rule from prettier source: force break when (1) more than 1 element, (2) every element is an array or object, (3) all elements are the same type, and (4) each inner element has more than 1 item.

Could you rework this to keep the width-based collapsing for simple arrays and only force-expand when that rule matches? I'll update issue #630 with the corrected spec.