Add missing <returns>/<param>/<summary>/<typeparam> tags and clean up
misused inheritdoc across 481 files so the documented API surface is
complete. Documentation-only (zero code lines changed). The 131 remaining
findings are inheritdoc-style warnings deliberately left to preserve
hand-written implementation rationale (plan-decision notes, race-condition
explanations).
- S7DriverPage.FormModel now preserves Tags through Form ↔ Options
translation (was hard-coding Tags = [] on every save, silently
destroying any tag list that operators had configured).
- Add FormModel_RoundTrip tests for OpcUaClient and Historian
mirror classes — both were translating Options ↔ form-model
entirely untested.
- Surface S7 Tags in the round-trip test so this regression
can't reach merge again.