fix(settings): preserve atomic path semantics

[Kibnet]

Summary

• Correct two atomic-path edge cases identified immediately after the 8.1.0 merge review.
• Publish patch version 8.1.1 to supersede 8.1.0.

Changes

• Treat numeric path segments as property names when the current JSON container is an object.
• Interpret numeric path segments as indexes only when the current container is an array.
• Reject sparse array indexes instead of silently appending at a different index.
• Reject traversal through existing scalar values without changing disk, backup or memory.
• Add regression tests and update README, changelog and package release notes.

Validation

• New regression tests before fix: 0 passed, 4 failed.
• New regression tests after fix: 5 passed, 0 failed.
• Full Windows suite: 42 passed, 1 expected non-Windows contract skip.
• Release build: 0 errors (2 pre-existing nullable warnings in ConfigTests).
• Packed WritableJsonConfiguration.8.1.1.nupkg and restored it into a clean consumer.
• Package consumer exercised numeric object keys, sparse-index rejection, atomic replacement, backup and read-back successfully.
• Local candidate SHA-256: 41E7570AB3E4F2DFCE36ADC43A242DF8CE63A50B31650C1E809060386768B4C6; CI will rebuild the delivery artifact from the merge commit.
• UI evidence: not applicable; this repository is a configuration library with no UI.

Risks / Rollback

• The behavior change is limited to opt-in atomic mode; legacy/default mode is unchanged.
• Sparse array writes now fail explicitly instead of writing the wrong element.
• NuGet packages are immutable. After publication, corrections require another patch version.

Links

• Follow-up to feat(settings): add opt-in atomic write mode #29 and release v8.1.0.
• Addresses the two automated review findings on numeric object keys and sparse array indexes.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-21T12:06:54.863623Z	1fcc4a8	PR opened

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