refactor(db): move maintenance store ownership

[TheSentinel454]

Current reconstructed head

Exact base: codex/issue-2-admin-moderation-store at 102fca801dfdb3bab867deb4fab615718d03c6fc
Exact head: codex/issue-2-maintenance-store at 3ea91d34db1b9feee9ae73a71622e86fe828ccdb

This current head removes crates/buzz-db/tests/store_ownership.rs; no replacement path-sensitive ownership test is introduced. Apart from removing that complete test-file diff, the production patch is byte-for-byte identical to the previously reviewed slice. This remains part of tracker #2 and the #17/#19 acceptance work.

Independent exact-head review from a separate clean Blox workstation found no issues. Current-head evidence passed formatting, strict buzz-db clippy, 111 non-PostgreSQL library tests with 200 PostgreSQL tests ignored, the observability source test, relay consumer compilation, exact ownership/unique-span review checks, and 3 focused partition validation unit tests (this slice moves no PostgreSQL test group) on native PostgreSQL where applicable.

Summary

Continue tracker #2 by moving the two remaining startup-maintenance Db facades to the modules that own their invariants: monthly partition creation to partition.rs, and NIP-33 d_tag materialization to event.rs.

The public Db API is unchanged. There is no dedicated domain issue for this tightly coupled maintenance slice; it completes two remaining ledger items while advancing #17 and #19.

Stack

• Tracker: TheSentinel454/buzz#2
• Domain issue: none; startup partition/event maintenance is tracker-led
• Test ownership acceptance: #17
• Span ownership acceptance: #19
• Exact base: codex/issue-2-admin-moderation-store at 7dbb399 (#6813)
• Exact head: codex/issue-2-maintenance-store at fcb55ab

Domain moved

• Db::ensure_future_partitions and its existing datastore span to partition.rs, beside the partition allowlist, validation, DDL implementation, and focused tests
• Db::backfill_d_tags, its unchanged event-table SQL, and its existing datastore span to event.rs

crates/buzz-db/src/lib.rs falls from 3,717 to 3,690 lines.

Non-goals

• Startup ordering, scheduling, logging, or error handling in the relay
• Partition ranges/allowlist/DDL, d_tag backfill SQL or event semantics, schema, locking, retries, timeouts, or client-visible behavior changes
• Moving general event-insertion materialization helpers
• Generic store traits, raw pool access, executor migration, or crate reorganization

Risk

Low semantic risk. Both public facades and their fixed-name spans moved intact; each continues to call or execute the same module-owned implementation using the same writer pool. No tests or production SQL changed.

Blox verification

Author workstation: buzz-tornquist-issue-2-store-stack (2046520), exact head 197549b3a28f2604d164208c4dd16e979458bb6c.

• cargo fmt --all --check
• git diff --check c684825860900357e017dd4102bc4df88dd6ec2e..HEAD
• cargo clippy -p buzz-db --all-targets -- -D warnings
• cargo clippy -p buzz-relay --all-targets -- -D warnings
• cargo test -p buzz-db --lib: 108 passed, 200 ignored, including all three partition validation tests and event materialization unit coverage
• cargo test -p buzz-db --test observability_source: 1 passed
• cargo test -p buzz-relay --lib: 909 passed, 48 ignored
• Commit hooks passed without bypass; the disposable workstation has no user signing key, so the commit itself is unsigned

Independent exact-head Blox review: pending.

Remaining tracker work

Next: deletion-store facades, the remaining cross-domain helper audit, and the final runtime-boundary/test assessment.

Superseded pre-comment restack verification

PR #6700 merged before publication completed. This layer was restacked onto current main through the exact parent named above; the final cumulative tip is 2ddcc8a. Cumulative author gates passed: formatting and diff checks; buzz-db and buzz-relay all-target clippy with -D warnings; DB lib 111 passed / 200 ignored; ownership 22/22; observability 1/1; the full isolated PostgreSQL domain matrix; and relay lib 910 passed / 49 ignored.

Result

No findings.

Exact revision and isolation

• Base: bcb1b423b7ac029759777209505800a757adc53b
• Head: 5c314af38a0707e5f932b6627ea688d1ac7c9d33
• Verified head parent and merge-base: exact base above
• Reviewer workstation: buzz-tornquist-pr-6814-final-review (2057668)

The fresh shallow workstation was clean and unclaimed, had no competing commands, and had no Buzz production relay credentials or ownership-report file.

Review conclusions

• ensure_future_partitions moves to partition.rs; backfill_d_tags and its unchanged NIP-33 UPDATE move to event.rs.
• Both public signatures, delegation/SQL, error behavior, fixed span names, and one-span ownership are preserved.
• The guard proves the maintenance facades no longer remain in lib.rs. At this head, its only remaining datastore spans are the runtime read_session_query_events and migrate spans.

Verification

• Diff check and Rust formatting: passed.
• Buzz DB and relay all-target clippy with -D warnings: passed.
• Buzz DB library: 111 passed, 200 ignored.
• Native PostgreSQL 17.11, migrations complete: three partition validation tests passed.
• An external exact-head facade probe invoked Db::ensure_future_partitions(0) and Db::backfill_d_tags() successfully against the migrated database (maintenance_backfilled=0).
• Final detached head remained clean; no duplicate datastore-span names were found.

Artifacts: pr-6814-final-review-artifacts.tgz, SHA-256 f16c5917bd9b238b332f6f4ecc0db49169c6455ddf1652baab170b8bfa715875. Archive and internal checksums were verified locally.

Comment-addressed restack

Review follow-up on #6777 removed only the low-value replaceable ownership source test. This PR was restacked onto its rewritten parent; its production patch is unchanged.

• Exact base: 7dbb399207515d12fc9b27036076e5d4f6bfb937
• Exact head: fcb55abb9018f03c74bb4ec52b32422ad253e62f
• Final cumulative tip: 6fa2f104d42c6ba85bdf62e7ccb74ceaf4a84f67
• Per-layer patch-ID and tree audits confirm this PR’s production diff is unchanged from its pre-comment head.
• Cumulative Blox gate: formatting and diff checks; strict buzz-db/buzz-relay Clippy; DB lib 111 passed / 200 ignored; ownership 21/21; observability 1/1; every moved PostgreSQL test; relay lib 910 passed / 49 ignored.
• Independent re-review at this exact head: no findings; fresh exact-parent/head Blox review passed fmt/diff, strict buzz-db/buzz-relay Clippy, DB lib and current ownership/observability/unique-span guards, 3 maintenance PostgreSQL tests, relay compilation, and the exact-head facade probe.