Make MMS file-transfer failures directly visible and copyable

[masarray]

Field problem

The engine already returns detailed failure text, but the Fault Record window stores it only in the row Detail property. The current table displays only Failed, forcing field debugging to rely on first-chance exceptions from Visual Studio.

Changes

• add a compact expandable Transfer diagnostics panel
• automatically select the failed row and open the panel when a download fails
• show device, endpoint, record, remote directory, companion files, timestamp, exact engine failure, protocol timeline, session/pump state, and request/response hex
• retain the existing long-duration row tooltip
• add one-click Copy diagnostics for pasting the complete evidence into support
• keep the panel collapsed during normal successful operation

The companion engine PR preserves the primary FileOpen/FileRead failure even if the best-effort FileClose also fails.

[chatgpt-codex-connector]

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