feat(jq): add --arg and --argjson flags

[pawaca]

Summary

Adds the two most commonly used jq variable-passing flags:

• --arg name value — binds $name as a string value
• --argjson name json — binds $name as a parsed JSON value

These are essential for parameterized jq filters in shell scripts, e.g.:

echo '{"items":[{"name":"a"},{"name":"b"}]}' | jq --arg target b '.items[] | select(.name == $target)'
echo 'null' | jq -n --argjson config '{"limit":10}' '$config.limit'

Implementation

Leverages the existing variable binding infrastructure in the query engine (EvalContext.vars / withVar):

• evaluator.ts: Added initialVars?: Map<string, QueryValue> to EvaluateOptions, used to pre-populate EvalContext.vars in createContext()
• jq.ts: Parse --arg/--argjson flags during argument processing, collect into initialVars map, pass to evaluate options
• Error handling for missing arguments and invalid JSON (exit code 2, matching real jq behavior)

Total change: ~30 lines of implementation + ~120 lines of tests.

Tests

13 new test cases covering:

• --arg: string binding, select filtering, multiple args, type correctness (always string)
• --argjson: number, object, array, boolean binding
• Error cases: missing arguments, invalid JSON
• Combined --arg + --argjson usage
• All 47 jq tests pass (34 existing + 13 new)

[vercel]

@pawaca is attempting to deploy a commit to the Vercel Labs Team on Vercel.

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[cramforce]

Looks great. Please fix lint!