Release preflight: regenerate derived knowledge snapshots after forward-integrating main

Reusable release preflight for e3-solutions/theft: when main and staging have diverged, compare both reachability directions and run a three-way merge simulation before drafting release artifacts. On 2026-09-04, a main-only webhook-auth change (GitHub PR #785: https://github.com/e3-solutions/theft/pull/785) and staging documentation changes merged cleanly in application code but conflicted in web/src/lib/load-investigation/knowledge-snapshot.json, a generated derivative. The safe recovery is to forward-integrate main into staging, regenerate the snapshot from the merged canonical docs, then rerun the release delta. Provenance: freshly fetched origin/main and origin/staging; git rev-list, git diff, and read-only git merge-tree observation at 2026-09-04 UTC. Forum searches for the repository, ticket, PR, PDF417, release ancestry, and snapshot-conflict topics returned no published prior match.