Stabilize preserved child record identities

[nicho1ab]

Pull Request Evidence

Governing issue and intended outcome

• Governing issue: Make preserved-artifact backfills safely repeatable #475. Issue Make preserved-artifact backfills safely repeatable #475 remains open after merge until corrected deployed production acceptance passes.
• Intended outcome: preserve stable child-record identity during preserved-artifact replay so a legitimate first normalization does not cause deterministic immediate-repeat writes.

Implementation scope

• Major files or components changed: preserved-artifact child-ID reconciliation, focused backfill regression coverage, and hosted-backfill developer documentation.
• Important behavior intentionally left unchanged or out of scope: schemas, migrations, connectors, live retrieval, reviewer UI presentation, authentication, facility-reference precedence, reviewer-created state, deployment configuration, statewide execution, and Issue Fix preserved-artifact backfill failures for 27 facilities #476.
• Reviewer UI regression contracts: RT-RC-004 and RT-RC-006 remain protected invariants. Stable source-derived identity, source-document relationships, reviewer-created-state separation, fixture relationships, and reviewer/audit relationships remain unchanged; no reviewer-facing presentation or interaction behavior changed.

Acceptance-criteria evidence

Acceptance criterion	Evidence and result
Reproduce second-pass child-ID instability	PASS - historical-fixture regression reproduces the old immediate-repeat update caused by positional allegation stable-ID reassignment.
Stable child-ID reconciliation	PASS - exact generated IDs are reserved first, followed by occurrence matching and deterministic fallback.
Immediate same-operation idempotence	PASS - corrected regression reports zero updates on immediate preserved-artifacts replay.
Equivalent operation idempotence	PASS - canonical-complaint-observations replay produces zero representation-only updates in the regression lifecycle.
Second apply idempotence	PASS - second apply performs zero source-derived writes in the regression lifecycle.
Genuine governed source changes	PASS - affected seeded-import regression continues to detect legitimate governed source changes.
Production acceptance	Pending - merged correction must still be deployed and prove 29-facility and full 312-facility repeat idempotence before #475 closes.

Validation and failure classification

Exact command	Result	Failure classification, if applicable
& 'C:\Repos\CCLD-complaints-poc.venv\Scripts\python.exe' -m pytest tests/unit/test_hosted_ccld_backfill.py::test_preserved_artifact_repeat_is_unchanged_when_extraction_adds_child -q	PASS - 1 passed in 1.61s	none
& 'C:\Repos\CCLD-complaints-poc.venv\Scripts\python.exe' -m pytest tests/unit/test_hosted_ccld_backfill.py tests/unit/test_hosted_seeded_corpus_import.py tests/unit/test_hosted_ccld_backfill_cli.py -q	PASS - 23 passed in 5.22s	none
& 'C:\Repos\CCLD-complaints-poc.venv\Scripts\python.exe' -m ruff check src/ccld_complaints/hosted_app/ccld_backfill.py tests/unit/test_hosted_ccld_backfill.py	PASS - All checks passed	none
& 'C:\Repos\CCLD-complaints-poc.venv\Scripts\python.exe' -m mypy src/ccld_complaints/hosted_app/ccld_backfill.py	PASS - no issues found in 1 source file	none
& 'C:\Repos\CCLD-complaints-poc.venv\Scripts\python.exe' scripts/check_docs.py	PASS - Documentation check passed	none
git diff --check	PASS - exit 0 with no output	none
& 'C:\Repos\CCLD-complaints-poc.venv\Scripts\python.exe' scripts/audit_portable_paths.py publication --field completion_report --input C:\tmp\issue475-completion-report.txt	PASS - Portable-path contract passed	none
& 'C:\Repos\CCLD-complaints-poc.venv\Scripts\python.exe' -m ruff format --check src/ccld_complaints/hosted_app/ccld_backfill.py tests/unit/test_hosted_ccld_backfill.py	FAIL - both files would be reformatted; no bulk reformat performed	pre-existing non-governing formatter drift

• Implementation-caused failures: None.
• Pre-existing failures: Supplemental Ruff format check reported broad formatter drift in the two affected files; no unrelated bulk reformat was performed.
• Environmental failures: None.
• Tests intentionally not run and why: Full local suite intentionally not run because this is a narrow focused correction; required PR CI provides repository-wide validation.

UI and accessibility evidence (when applicable)

Not applicable - no UI or accessibility change.

Reviewer-facing redesign artifact classification (when applicable)

Not applicable - no reviewer-facing removal, merge, rename, relocation, replacement, or redesign.

Documentation, assumptions, and remaining risks

• Documentation impact: hosted-backfill documentation now specifies deterministic preserved child-ID reconciliation.
• Assumptions and limitations: local regression and focused validation pass, but production repeat-idempotence acceptance has not yet been rerun against this correction.
• Remaining risks or follow-up: deploy the merged correction and rerun the retained 29-facility dry/apply/repeat lifecycle plus the full 312-facility preserved-artifact repeat before closing Make preserved-artifact backfills safely repeatable #475.

Governed-boundary review

Governed boundary	Status	Specific explanation or evidence
Schemas and migrations	No change	No schema or migration changed.
Ingestion and source-connector contracts	No change	No source connector or retrieval contract changed.
Security and privacy	No change	No credentials, authentication, authorization, private-data, or secret-handling behavior changed.
Production data and correction behavior	Authorized change	Preserved-artifact backfill now reconciles child stable IDs deterministically instead of positional lexical reassignment.
Deployment and infrastructure	No change	No QNAP, Compose, Cloudflare, container, host, or infrastructure configuration changed.
Repository governance	No change	No repository governance files or policies changed.
Required GitHub workflows and checks	No change	validate, docs-check, fixtures, and security remain required.
Tests or checks weakened to obtain passage	Authorized change	tests/unit/test_hosted_ccld_backfill.py changed to strengthen regression coverage for the discovered child-ID reconciliation defect. No assertion, validation requirement, test, or required check was removed, skipped, relaxed, or weakened to obtain passage.

Required GitHub checks

• validate
• docs-check
• fixtures
• security