Support dot notation for list indices in skip verification paths

[bentsku]

Motivation

Stacked on #27.

Skip paths using dot notation for list indices, like $..aaa.1, $..aaa..0 or $..aaa.0..aab.1, never matched anything, on jsonpath-ng 1.7 or 1.9. jsonpath-ng only matches Fields against dicts. The existing tests didn't catch this because each dot-notation assertion ran after a bracket-notation assertion on the same session, which had already removed the values. Skip paths using this syntax have been silently not applied.

Changes

• After parsing a skip path, replace digits-only Fields with a _FieldOrIndex node. It acts as a list index when applied to a list, and as a regular key otherwise. This has to be decided at match time, since $.a.1 and $.a.'1' parse to the same AST, so numeric dict keys keep working.
• Rewrite the list skip-path tests to use a new session for every assertion, parametrized over bracket and dot notation. Add tests for numeric dict keys and out-of-range dot indices.

Known limitation: jsonpath-ng can't parse consecutive numeric fields like $..aaa.2.0, because 2.0 is lexed as a float. Use $..aaa.2[0] instead. This is noted in the docstring.

🤖 Generated with Claude Code

[bentsku]

Closing: $.a.1 isn't valid JSONPath (RFC 9535 requires bracket notation for indices), and no snapshot skip path in localstack uses it, so we won't add a custom dialect. The test cleanup (a new session per assertion, so tests can't pass on state already mutated by an earlier assertion) is folded into #27.