sanity_check raises UnwrapFailedError on malformed JSON instead of returning validation error

[shekharhimanshu]

When running sanity_check() on a dataset containing a malformed JSON file, the function raises an UnwrapFailedError exception instead of gracefully reporting the JSON parsing error as a validation failure.

Expected Behavior
The sanity check should catch JSON parsing errors and report them as validation errors in the SanityResult, e.g.:
Validation Error: Invalid JSON in <filename> at line 8, column 5 - Expecting property name enclosed in double quotes

Actual Behavior
An unhandled UnwrapFailedError exception is raised, which makes it difficult for callers to:

• Understand what went wrong (the actual JSONDecodeError is buried in the exception chain)
• Handle validation failures gracefully
• Report meaningful error messages to users

Root Cause
In in t4_devkit/sanity/format/base.py, the check method calls .unwrap() without handling Failure:

def check(self, context: SanityContext) -> list[Reason] | None:
    filepath = context.to_schema_file(self.schema).unwrap()

    if self.schema.is_optional() and not filepath.exists():
        return None

    records = load_json_safe(filepath)
    return _build_records(self.schema, records.unwrap())  # ← crashes here on malformed JSON

Suggested Fix
Handle the Failure case before calling .unwrap():

def check(self, context: SanityContext) -> list[Reason] | None:
    filepath_result = context.to_schema_file(self.schema)
    if isinstance(filepath_result, Failure):
        return [Reason(f"Failed to resolve schema file: {filepath_result.failure()}")]
    filepath = filepath_result.unwrap()

    if self.schema.is_optional() and not filepath.exists():
        return None

    records = load_json_safe(filepath)
    if isinstance(records, Failure):
        return [Reason(f"Failed to parse {filepath.name}: {records.failure()}")]
    return _build_records(self.schema, records.unwrap())

Environment
t4-devkit version: 0.5.2
Python version: 3.12