Repair sync-content verification test after staged-import helper removal

Problem

The maintained Django suite cannot collect because scripts/tests/test_sync_content_verify.py imports both content_sync.tests.helpers and scripts.prod.sync_content_verify, which were intentionally removed with the retired DataTalksClub/content staged-import pipeline in 1cd976a4. scripts/content.py still exposes checkout and drift commands that dispatch to that missing verifier.

This is not a request to resurrect the retired pipeline. It is a baseline repair: remove the orphaned test/CLI surface while retaining every verification invariant that still applies to the supported database-owned sync paths.

Authority

• _docs/architecture/database-only-content.md — public content is database-owned; sync may write rows directly, but a checked-in/staged projection is not a runtime authority.
• _docs/runbooks/data-ingest.md — current ingest entry points and source ownership.
• _docs/specs/10-verification-strategy.md — maintained Django gates must collect and pass; a failed gate is not waived.
• _docs/PROCESS.md — selective evidence does not permit a required failed tier to be skipped.

Product/architecture decision

Do not restore content_sync.tests.helpers, content_sync.dtc_content, or scripts/prod/sync_content_verify.py. The removed helper was coupled to the removed dtc_content fixture tree and verifier, not a supported reusable test boundary. Restoring it would make collection green by reviving code for the wrong architecture.

The orphaned verifier test may be removed or replaced only after its still-relevant guarantees are explicitly mapped to current tests and any real gaps are ported to the owning current boundary. Cases that existed solely to compare a retired ContentRelease staged projection with that source checkout are obsolete behavior, not coverage to recreate.

Scope

• Reconcile scripts/tests/test_sync_content_verify.py with the removal commit so no maintained test imports or executes deleted staged-import code.
• Audit the old test cases and record their disposition in the implementation handoff:
  • current equivalent already covered, with the exact test named;
  • ported to the current owning test module; or
  • obsolete with the retired staged verifier, with the reason.
• Preserve/port the applicable guarantees: source scoping; discover/create/update/delete behavior; revision/checksum provenance; idempotence; fail-closed invalid input/checkout behavior; atomic failure; current offline/no-network paths; and no cross-source deletion.
• Remove the stale scripts/content.py checkout and drift command paths and their parser expectations, or retarget them only if a currently supported equivalent already exists. No command advertised by scripts/content.py --help may point at a missing module.
• Update only directly affected evergreen command/runbook references so operators are not told to invoke removed commands.
• Add a bounded regression that catches dangling production-script/test imports or advertised scripts/content.py subcommands before the full suite reaches collection.

Non-goals

• Recreating the deleted staged-import adapter, fixtures, projection comparator, or ContentRelease-based editorial workflow.
• Designing a new generic drift-reporting product or changing the community_base.content_sync API.
• Changing public content, parser output, database rows, source registrations, course curriculum ingest, or production data.
• Weakening, skipping, quarantining, or excluding the maintained Django suite.
• Refactoring unrelated legacy importers or resolving all historical runbook drift.

Dependencies and blocked work

• No open implementation dependency. Commit 1cd976a4 is historical context, not a dependency to reverse.
• This repair blocks final full-Django evidence for #425 and any other candidate currently encountering the same baseline collection failure. Those candidates must rebase/freeze and rerun against the repaired baseline; their selective-CI evidence cannot waive this failure.
• Keep the change in this repository. If implementation unexpectedly requires a community-base change, stop and re-scope first; that shared package would require its own contract and both consumer suites per AGENTS.md.

Acceptance criteria

• The maintained Django test suite collects without importing content_sync.tests.helpers, content_sync.dtc_content, or scripts.prod.sync_content_verify.
• The implementation handoff contains a case-by-case mapping of the old verifier coverage to named current tests, newly ported tests, or a precise retired-only rationale; the old test is not simply skipped, renamed out of discovery, or deleted without that mapping.
• Current tests prove source-local create/update/delete, checksum/revision provenance, idempotence, invalid-input atomicity, and protection from deleting another source's rows.
• Current checkout-backed paths retain their existing dirty/revision/refusal and offline/no-network coverage; no test reaches GitHub or production data.
• uv run --frozen python scripts/content.py --help advertises only executable, supported workflows, and every advertised subcommand has a focused dispatch/parser test.
• Repository search finds no live code, tests, or operator instructions that invoke the removed verifier/helper. Historical audit prose may name it as history when clearly marked.
• No retired staged-import module, fixture tree, hardcoded public-content fallback, or checked-in projection is restored.
• Focused current sync/parser/command tests pass from synthetic local fixtures.
• uv run --frozen python scripts/ci.py test collects and passes in full; no exclusion, quarantine, or collection-ignore is added.

Repository and operations scenarios

1. From a clean test environment, collect and run the focused sync/parser/command tests; they use synthetic fixtures and no network or operator staging tree.
2. Exercise every scripts/content.py subcommand parser/dispatch contract and confirm none resolves a deleted file.
3. Run the full maintained Django tier and confirm collection reaches execution and passes.
4. Inspect the coverage-disposition record against every former test class (Agreement, Drift, MediaAsymmetry, RevisionStatus, Scope, Refusal, WorkingCopyIndependence, CheckoutPlan, ReadOnly, ReportShape, Convention). Reject unexplained loss.

Browser scenarios

Not applicable. This issue changes test/CLI wiring and directly affected operator documentation only; it must not alter a rendered route. Per _docs/PROCESS.md, the tester should classify screenshot evidence as not_applicable with this reason and run the applicable backend-only Playwright smoke tier selected by the frozen verification graph.

Start with scripts/tests/test_sync_content_verify.py, scripts/content.py, commit 1cd976a4, and the listed architecture, runbook, verification, and process documents. Run the focused sync/parser/command tests and inspect the current Django tests before mapping every former verifier case to a named equivalent, a ported test, or a retired-only rationale. Done means no dangling imports or advertised missing commands, required invariants remain covered, and uv run --frozen python scripts/ci.py test collects and passes.