docs: seventh-pass archive unsafe legacy references

documentation/archive/README.md

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+# Documentation Archive Index
+
+This directory preserves completed projects, superseded proposals, historical task logs, and legacy technical references.
+
+Archived files are not authoritative for current implementation. Start with `documentation/README__Docs_Index.md` and the active module/guides directory.
+
+## Categories
+
+### Completed or Superseded Projects
+
+Files prefixed with `PROJECT__` document completed implementation phases or superseded project plans.
+
+### Historical Proposals
+
+Files prefixed with `PROPOSAL__` preserve design ideas that are not the current implementation source.
+
+### Task History
+
+Files prefixed with `TODO__Agents__ARCHIVE_` contain completed task history by month.
+
+### Legacy References
+
+Files prefixed with `REFERENCE__Legacy_` are retained for historical context but contain pre-V3, pre-runes, or otherwise superseded guidance.
+
+Do not copy implementation patterns from legacy references without validating them against current source and active guides.
+
+## Restore Policy
+
+Move an archived doc back to the active documentation root only when:
+
+1. Its subject is active again.
+2. Its content has been reviewed against current source.
+3. Legacy paths, IDs, stores, and API conventions have been updated.
+4. It is added to `documentation/README__Docs_Index.md`.