Seed the compliance suites: self-aggregating evolve, DCB tag query/consistency, AssignTagWhere (P3.1b)

[jeremydmiller]

Part of #5110. Blocked by P3.1a (the seam).

Port the three highest-overlap Marten↔Polecat test pairs into abstract compliance suites written once against EventStoreComplianceFixture<,>:

• SelfAggregatingEvolveCompliance (from EventSourcingTests/Aggregation/self_aggregating_evolve_method.cs; 84% line overlap with the Polecat mirror, 8/8 methods)
• DcbTagQueryAndConsistencyCompliance (from EventSourcingTests/Dcb/dcb_tag_query_and_consistency_tests.cs; 79%, 24/26)
• AssignTagWhereCompliance (from EventSourcingTests/Dcb/assign_tag_where_tests.cs; 72%, 6/6)

Marten-side: concrete subclasses in EventSourcingTests consume them through the Marten fixture; the original Marten test files are then retired (program steps 1–2: write on the standard base, retire the old).

Strongest-assertion-wins fixes (decision D5) — these are real findings, not style

1. Inline-snapshot tests must assert document persistence via LoadDocumentAsync — the Polecat mirror reads back via AggregateStreamAsync (live re-fold) and would pass with a broken inline projection.
2. assign_tag_where_by_stream_id keeps Marten's e.StreamId == stream1 assertion (the Polecat mirror weakened it to Data-type checks).
3. Adopt Polecat's can_query_events_across_distinct_tag_types_with_or regression test (INNER JOIN bug) — Marten gains this coverage on day one; if Marten fails it, that is a product bug to fix, not a test to soften.

Verification: EventSourcingTests net9.0 full suite; the retired originals' coverage is a strict subset of the new suites.

🤖 Generated with Claude Code

[jeremydmiller]

Landed in #5122, merged to master as 4cfe6c5a2. (GitHub only auto-closed #5111 — the PR body listed the four in one Closes clause and only the first is parsed.)