[ADR-015] Schema Migration Ledger

[ohdearquant]

Summary

Update the versioned migration ledger mechanics, tests, comments, and transaction behavior after domain schema clusters have defined the concrete migrations.

Source ADRs

• F082 ADR-015 (MAJ): Production MIGRATIONS contains four VersionedMigration entries, V1-V4, ending at dedupe_graph_edge_triples (from audit-foundation/e6/ADR-015.md)
• F083 ADR-015 (MAJ): Migration tests treat V4 as the latest version (assert_eq!(version, 4)), and the idempotency test repeats that expectation (from audit-foundation/e6/ADR-015.md)
• F084 ADR-015 (MAJ): Each migration is run with conn.transaction() (from audit-foundation/e6/ADR-015.md)
• F085 ADR-015 (MIN): The versioned migration system comment still says ADR-022. (from audit-foundation/e6/ADR-015.md)

Files affected

• crates/khive-db/src/migrations.rs (506 sampled LOC)

Acceptance criteria

• All source findings listed above are addressed exactly once in this cluster.
• Public types, handlers, schema, and docs touched by the affected files agree on the ADR contract.
• Regression tests cover happy path and edge cases for the changed public APIs or schema behavior.
• cargo test -p khive-db passes.
• cargo clippy --workspace -- -D warnings passes.
• make ci passes.

Dependencies

• Depends on: #[ADR-001] Entity Kind and Type Contract
• Depends on: #[ADR-002] Edge Ontology, Lifecycle, and Bulk Link Semantics
• Depends on: #[ADR-004] Note Kind, Storage, and Curation Operations
• Depends on: #[ADR-004] Event Observable and Provenance Model
• Depends on: #[ADR-004] GTD Pack Schema Plan and Lifecycle Audit
• Depends on: #[ADR-043] Embedding Model Registry and Vector Engine Migration
• Depends on: #[ADR-025] Event-Sourced Proposals
• Blocks: none

LOC estimate

~80 lines added/30 removed; 1 existing affected file(s) sampled at 506 current LOC via wc -l, plus 0 new/planned path(s).

Risk notes

• Same-file dependencies must merge first; dependency list includes the exact overlapping paths.

Auto-generated by ADR alignment triage

[ohdearquant]

Landed in main via PR #349 (integration of cluster c24 — original cluster PR was #358). Tracker complete.