feat(episteme): preserve multiplicity metadata on consolidated Fact (revive branch)

[forkwright]

Branch feat/episteme-fact-multiplicity was 394 commits behind main and never merged despite issue #3634 being closed. The work is real and complete (428 additions / 22 deletions across 43 files).

What the branch does

Adds source_count: usize to FactProvenance and propagates through the knowledge store, query builders, marshalling, and recall scoring:

• eidos: add source_count to FactProvenance with serde default 1
• episteme: add source_count to ConsolidatedFact and persist it
• episteme: bump knowledge schema v6 → v7 with migration
• episteme: update all Datalog scripts and query builders
• episteme: include source_count in recall score (logarithmic, default weight 0)
• episteme: tie-break conflict resolution by source_count when confidence is equal
• integration-tests: update schema version assertion

Why this issue

Branch deleted as part of spotless-pass hygiene (2026-05-26). The original branch commit was: feat(episteme): preserve multiplicity metadata on consolidated Fact (gate-passed, closes #3634). Needs rebase onto current main before PR.

Action

Rebase feat/episteme-fact-multiplicity commit onto current main, verify CI green, open PR.

[forkwright]

Decision (operator-confirmed 2026-06-03): close as superseded; the premise is inverted. Verified: PR #3665 (the parked feat/episteme-fact-multiplicity branch) was CLOSED/rejected, not lost. Issue #3634 was resolved by the merged PR #3692, which deliberately chose a fact_multiplicity side-index (design option 3) over the branch's source_count-on-FactProvenance (option 1) to keep Fact schema stable across 50+ construction sites. FactProvenance has no source_count today (eidos/src/knowledge/fact.rs:33); schema is at v13 vs the branch's v6→v7 (~7 versions stale). Reviving the branch would re-introduce rejected, conflicting code.

The genuine remaining gap (merged get_fact_multiplicity is consulted only from tests, not recall/conflict) is tracked in a fresh scoped issue. Closing.