bug: oversized numeric placeholder indices raise instead of using the missing-value fallback #91

Problem

Following #76, _lookup_path checks segment.isdecimal() before converting a list index with int(segment). This rejects superscript digits correctly, but an all-decimal segment longer than Python's configured integer-string conversion limit still raises ValueError. The exception bypasses both the missing-path marker and default(...).

Confirmed on main 7570cfe with the default 4,300-digit limit. Priority: low (P3). This is an extreme malformed-input edge case and is not a reason to reopen #61 or revert #76.

Reproduction

import sys
from stuntdouble import resolve_output

limit = sys.get_int_max_str_digits()
assert limit > 0  # Default is 4300; this reproducer requires the limit enabled.
index = "9" * (limit + 1)
template = "{{input.items." + index + " | default('missing')}}"
resolve_output(template, input_data={"items": []})
# Actual: ValueError: Exceeds the limit (...) for integer string conversion
# Expected: "missing"

Acceptance

• Treat an index that cannot be converted as an unresolved path segment, preserving the existing marker/default behavior.
• Cover both input and config references, with and without a default, and list/tuple traversal.
• Preserve normal indices and supported Unicode decimal digits.
• Do not disable or globally change Python's integer-conversion limit. Regression tests should remain valid when the environment configures a different limit.

Relevant files: src/stuntdouble/resolving.py, tests/test_resolving.py.

Filed with Codex assistance during a maintainer issue audit.