Generalize record completeness to a 3-state model and make it a hard block on modifying completed rows

[DutchJaFO]

Background

Migration006_RecordCompleteness (#55) added a boolean IsComplete + JSON-array NoValueKnown to
Quotes/Sources/Characters/People, intended to protect a human-confirmed-complete record from
being silently overwritten by a later import. Verified against the actual current code: this
migration has not shipped in any release tag (v1.7.2 is latest) and isn't merged to main yet —
only present on this feature branch, so nothing here needs to preserve compatibility with a released
database. Also verified: nothing in the codebase currently reads either column to make a decision
— they're written once at insert time (hardcoded 0/'[]') and never consulted again.
Quotes.UpdateOnNewestWins excludes them from its SET list, which is the only place they're
referenced at all outside entity property declarations. Conversations/StageDirections/SoundCues
have neither column.

This issue emerged while scoping #162 (Source field decidability): giving Source's Title/Type/
Date a Modify path means, for the first time, the staging engine can attempt to overwrite a field on
a record a human has already reviewed — and that must never happen silently, for the whole batch, not
just the one affected action. This is a general mechanism every future "entity X decidability" issue
needs (Character, Person, Conversation, StageDirection, SoundCue), so it's being built once, generically,
here, rather than reinvented per entity. #162 depends on this issue and only consumes what it builds.

What needs to be done

1. Replace IsComplete BIT with a 3-state CompletenessStatus enum (Incomplete/NeedsReview/
   Complete) on Quotes/Sources/Characters/People, editing Migration006_RecordCompleteness
   in place (safe — unshipped). Add both CompletenessStatus and NoValueKnown to Conversations/
   StageDirections/SoundCues in the same migration, which have neither column today. Update the
   fresh-database baseline schema in the same commit; add a schema-drift test per the existing
   baseline/incremental-replay convention.
2. CompletenessStatus lives in Quotinator.Data.Entities (Data-owned, [SafeValue<TEnum?>]-backed
   per ADR 008, registered by the base DatabaseConfiguration) since it's meant to be reused by any
   consuming project's entities, not Quotinator-domain-specific — same pattern as ImportActionStatus/
   ImportBatchStatus. The migrations that add the columns stay in each table's owning project.
3. New domain-agnostic CompletenessGuard static class in Quotinator.Data.Import (alongside
   FieldMergeResolver): ShouldBlock(CompletenessStatus status, IReadOnlySet<string> changedFields)
   — returns true only when status == Complete; ComputeNextStatus(CompletenessStatus current, IReadOnlyList<string> noValueKnownAfterApply) — computes the Incomplete → NeedsReview
   auto-transition (every field now has a known value, while status was still Incomplete; never
   auto-transitions away from Complete).
4. New ImportActionStatus.Blocked (Data-owned enum, System_ImportActions.Status CHECK constraint
   widened via a rebuild-under-temp-name migration per database-conventions.md's
   Migration004_ImportBatchTypeUserSeed precedent). An entity planner stages Blocked instead of
   Modify when CompletenessGuard.ShouldBlock returns true for the target row.
5. ImportActionResolutionCoordinator.TryApplyBatchAsync (Quotinator.Data.Import) widens its
   whole-batch guard from Status == Pending to Status is Pending or Blocked — a batch containing
   even one unresolved Blocked action holds entirely; no action in it applies, including unrelated,
   otherwise-ready actions, until every Blocked action is explicitly decided.
6. SystemImportAction gains a new nullable, entity-agnostic column: MarkCompletenessAs
   (CompletenessStatus?). Deciding any import action, for any entity type, can optionally set the
   target record's CompletenessStatus directly (most usefully Complete) as part of that same
   decision — always available, not only when resolving a Blocked action. ConflictDecisionRequest
   gains a matching shared MarkCompletenessAs property. SqliteImportActionService.DecideAsync →
   ImportActionResolutionCoordinator.DecideAsync → SystemImportActionWriter.MarkDecidedAsync each
   thread the value through to persist it alongside MergedFields/Status → Decided.
7. ApplyResolvedActionAsync's per-entity branches read action.MarkCompletenessAs back at apply
   time: if set, write it directly as the row's CompletenessStatus (explicit human override always
   wins, regardless of current status); if not set, fall back to
   CompletenessGuard.ComputeNextStatus(existingRow.CompletenessStatus, computedNoValueKnown). This
   applies to Quote's own existing apply path too, not only to entity types made decidable by later
   issues — Quote already has both columns from Schema: record completeness flag and per-field verified-absent markers #55.
8. DecideAsync/UndoDecisionAsync/TryReverseBatchAsync behaviour for Blocked otherwise matches
   Pending: deciding a Blocked action is permitted; undo reverts unconditionally to Pending;
   reversing a batch containing an unresolved Blocked action is refused until it's resolved (already
   true today via the existing Status != Applied guard — no code change needed there).

Expected tests

Test class	Test method	Starts
New: Quotinator.Data.Tests	CompletenessGuard_ShouldBlock_OnlyTrueWhenStatusIsComplete	❌
New: Quotinator.Data.Tests	CompletenessGuard_ComputeNextStatus_IncompleteToNeedsReviewWhenNoValueKnownEmpty	❌
New: Quotinator.Data.Tests	CompletenessGuard_ComputeNextStatus_NeverDemotesFromComplete	❌
New: Quotinator.Data.Tests	Migration_BlockedStatus_CheckConstraintAcceptsNewValue	❌
New: Quotinator.Data.Tests	Baseline_And_IncrementalReplay_ProduceIdenticalCompletenessSchema	❌
New: Quotinator.Data.Tests	TryApplyBatchAsync_BlockedActionInBatch_HoldsEntireBatch	❌
New: Quotinator.Data.Tests	TryApplyBatchAsync_BlockedActionResolved_UnrelatedActionsThenApply	❌
New: Quotinator.Engine.Tests	ApplyBatchAsync_MarkCompletenessAsProvided_OverridesAutoCompute	❌
New: Quotinator.Engine.Tests	ApplyBatchAsync_MarkCompletenessAsOmitted_FallsBackToAutoCompute	❌
New: Quotinator.Engine.Tests	ApplyBatchAsync_QuoteAlreadyComplete_MarkCompletenessAsOmitted_StatusUnchanged	❌
New: Quotinator.Api.Tests	DecideImportAction_MarkCompletenessAsComplete_PersistsAtApply	❌

Definition of done

• All expected tests listed above start red before implementation
• All requirements implemented
• All expected tests pass (green)
• No regression in related tests
• Findings summarised in a closing comment

[DutchJaFO]

Released in v1.8.0.

#	Status	Requirement	Method	Verification
1-3	✅	CompletenessGuard.ShouldBlock/ComputeNextStatus correct, including the never-demote-Complete rule	Unit test	CompletenessGuardTests
4-5	✅	Blocked status accepted by widened CHECK; an already-migrated database (Data-version 9) upgrades correctly	Unit test	DatabaseInitializerOwnershipTests.InitialiseAsync_ExistingDatabaseAtDataVersion9_UpgradesSystemImportActionsWithBlockedAndMarkCompletenessAs — direct regression test for a real bug found via T1 (an in-place migration edit that silently never re-ran against an already-migrated dev DB)
6-7	✅	A Blocked action holds the whole batch; resolves and the rest applies normally	Unit test	ImportActionResolutionCoordinatorTests.TryApplyBatchAsync_BlockedActionInBatch_HoldsEntireBatch and sibling
8-11	✅	MarkCompletenessAs override/auto-compute correctly threaded decide→apply, including Quote's own path	Unit test	SqliteImportActionServiceTests, QuoteImportServiceTests, ConflictResolutionTests
12	✅	Build/tests clean	Live	1158 tests, 0 warnings, 0 errors
13-14	✅	T1/T2 — migration upgrade path live; full stage→decide→apply cycle proving a Complete row's field genuinely can't be silently overwritten and the whole batch is genuinely held	Live	Confirmed; found and fixed two more real bugs live (missing [JsonConverter] on CompletenessStatus, and POST /import's 200/202 decision ignoring non-Quote Blocked actions)