chore(repo): keep only current main snapshot

History squashed to one root commit to permanently drop old branch history and objects.

dependency_whitelist.md

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+# Dependency Whitelist
+
+Use this file only when a same-level or lateral dependency is unavoidable.
+
+Entry format:
+- requester: `<layer>/<module>`
+- target: `<layer>/<module>`
+- reason: short technical justification
+- owner: person/team
+- expiry: YYYY-MM-DD (must be reviewed before expiry)
+
+Current entries:
+- none