fix: IndexError when raising T0412/T2009 JExceptions with 3 format args

[abhi-0203]

Summary

Fix IndexError: Replacement index 2 out of range for positional args tuple when raising T0412 or T2009 JExceptions.

Root Cause

JException.msg() had a fixed signature (error, location, arg1, arg2) but T0412 and T2009 error templates have 3 placeholders:

• T0412: "Argument {{index}} of Object {{token}} must be an array of {{type}}"
• T2009: "The values {{value}} and {{value2}} either side of operator {{token}} must be of the same data type"

When str.format(arg1, arg2) was called with these templates, Python raised IndexError because the 3rd {} had no corresponding argument.

Fix

1. Changed JException.msg() to accept *args — variadic, works for 1, 2, 3, or more args
2. Updated T0412 raise in signature.py to pass 3 args: (arg_index + 1, function_name, param.subtype)
3. Updated T2009 raise in jsonata.py to pass 3 args: (lhs, op, rhs)
4. Added JException.extra attribute to store the 3rd argument (needed for get_detailed_error_message())
5. get_detailed_error_message() now passes all 3 stored args correctly

Test

import jsonata
expr = jsonata.Jsonata("$sum(x)")
expr.evaluate({"x": ["y"]})  # Was: IndexError, Now: JException "Argument 1 of Object sum must be an array of n"
expr2 = jsonata.Jsonata('"foo" > 3')
expr2.evaluate({})  # Was: IndexError, Now: JException "The values foo and > either side of operator 3 must be of the same data type"

Closes #42

[Copilot]

Copilot review overview

🟡 Changes recommended

T2009 arguments are misordered, and exceptions using omitted formatting arguments now raise IndexError.

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Review effort: Balanced
Findings: 1 · 1 · 1

Open (3)

• Preserve JException default arguments and variadic compatibility · New
• Correct T2009 exception argument ordering · New
• Add regression tests for T0412 and T2009 messages · New

What changed in this PR

Fixes three-argument formatting for T0412 and T2009 exceptions.

Changes:

• Makes JException formatting variadic and stores a third argument.
• Supplies three formatting values at affected call sites.
• Updates detailed exception rendering.

File	Description
src/​jsonata/​signature.py	Supplies T0412 index, function, and subtype.
src/​jsonata/​jsonata.py	Supplies T2009 comparison details.
src/​jsonata/​jexception.py	Adds variadic formatting and third-argument storage.

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