Add standalone mangle-lint CLI tool

[danielostrow]

mangle-lint

• Adds a new lint/ package and cmd/mangle-lint binary — a standalone linter for Mangle .mg files
• Reuses the existing analysis infrastructure (validation, temporal recursion, stratification, bounds checking) and surfaces findings as lint results
• Adds 6 new lint checks on top of existing analysis:

Rule	Severity	Description
unused-predicate	Warning	Declared predicates that are never referenced
missing-doc	Info	Predicates without documentation descriptors
naming-convention	Warning	Enforces snake_case predicates and uppercase variables
singleton-variable	Warning	Variables appearing only once in a clause (likely typos)
overly-complex-rule	Info	Rules exceeding a configurable premise threshold
dead-code	Info	IDB predicates whose results are never consumed

• Supports text and JSON output formats
• Rules are individually toggleable via -disable / -enable flags
• Exit codes: 0 (clean/info), 1 (warnings), 2 (errors)

Usage

# Lint files
mangle-lint examples/*.mg

# JSON output, warnings only
mangle-lint -format json -severity warning examples/*.mg

# Disable specific rules
mangle-lint -disable missing-doc,dead-code examples/*.mg

# List all available rules
mangle-lint -list-rules

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[danielostrow]

@burakemir can you please review this linter? I wanted to separate this as a separate cmd as opposed to debugging on compiler feedback alone.