P7.1 #446: collapse duplicate SCL cards and harden diagnostics

[masarray]

Stacked field-fix milestone for #446 based on PR #454.

Field defects reproduced from 7SX85 SCD test

1. one physical/logical IED appeared as two Engineering cards because ARSAS projected every SCL AccessPoint workspace as a separate IED card;
2. an SCL with no direct ConnectedAP MMS IP produced "No endpoint" even when ARSAS had a previously successful endpoint for the exact IEDName;
3. Copy Diagnostic threw ArgumentException: An item with the same key has already been added. Key: No endpoint because TCP probe evidence was keyed by display endpoint text.

Fix

• collapse SCL AccessPoint workspaces to one primary Engineering card per IEDName;
• choose the primary AP deterministically: usable MMS endpoint, Server-bearing AP, report/DataSet authority, model coverage;
• reuse an existing same-IED card when safe instead of creating a second card;
• preserve current proven endpoint identity when SCL is offline-only;
• when the SCL has no direct MMS endpoint, restore the most recent successful exact-IEDName endpoint from local preferences, while explicitly requiring a fresh association before live use;
• remove redundant inactive SCL cards from the same source/IED identity;
• key diagnostic TCP probe evidence by DeviceId rather than endpoint text;
• add a probe-free emergency diagnostic fallback so malformed workspace state cannot make support diagnostics fail a second time.

Safety

• nested GSE/SMV addresses are still not promoted to MMS endpoints;
• no endpoint is fabricated from SCL when no direct MMS address exists;
• remembered endpoint evidence is local history for the exact IEDName and is revalidated through a fresh MMS association;
• connected/monitoring cards are never removed by duplicate cleanup;
• this patch does not change reporting/RCB acquisition semantics from P7.

Regression

• two offline cards sharing No endpoint can build a diagnostic report;
• emergency diagnostics preserve evidence without probes;
• source guard locks one-card-per-IED SCL projection and remembered-endpoint restoration;
• Copy Diagnostic guard prevents endpoint-text dictionary identity from returning.