Improved bash json parser

[rcannood]

Describe your changes

Rewrites the Bash JSON parser (ViashParseJson.sh) as a recursive descent parser modelled after the Scala ViashParseJson.scala. The old line-based regex parser silently failed on compact JSON and had fragile string/array handling.

Related issue(s)

Part of the switch_to_arrays branch (PR #762).

Type of Change

• Major change (non-breaking change which modifies existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Changes

Problems with the old parser:

• Silent failure on compact/minified JSON (assumed one key-value pair per line)
• Array parsing logic duplicated 3×
• Embedded commas, colons, braces in strings could confuse regex patterns
• Unrecognised lines silently skipped

New parser: Recursive descent with _viash_peek/_viash_consume primitives, type-specific parsers (_viash_parse_string, _viash_parse_number, etc.), serialization functions for deep nesting, and proper error reporting. Input is pre-split into a character array via fold -w1 for O(1) access.

Performance:

Dimension	Old	New
500 KV pairs	573ms	481ms
500 array elements	1040ms	295ms
10k char strings	N/A	177ms

Compatibility

• Bash 3.2+ (macOS default) — no declare -g, local -n, or readarray
• All 64 parser tests + 70 render tests pass

Checklist

• I have read the CONTRIBUTING doc.
• I have performed a self-review of my code.
• My code follows the code style of this project.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• Proposed changes are described in the CHANGELOG.md.

[hcannoodt]

it's starting to become all a bit crazy ...