Telemetry baseline: durable analytics outbox, session tracking, UI-framework marker

[johnml1135]

Summary

Establishes a FieldWorks-only telemetry baseline (openspec change: telemetry-migration-baseline) ahead of the planned Avalonia UI migration, so there's a "legacy WinForms" usage/crash/session baseline to compare against later.

• AnalyticsOutbox (Src/Common/FwUtils/AnalyticsOutbox.cs): a durable local queue in front of DesktopAnalytics.Analytics.Track/ReportException. Today, an event generated while offline is silently dropped (DesktopAnalytics is fire-and-forget with no retry). The outbox persists each event as its own small JSON file, flushes on enqueue/startup/shutdown, and re-checks consent at flush time (not just enqueue time) so revoking consent stops even already-queued data from going out.
• All 6 existing Analytics.Track/ReportException call sites are migrated to the new facade (FieldWorks.cs, AreaListener.cs, TrackingHelper.cs, ConcordanceContainer.cs, ConfigureInterlinDialog.cs, ObtainProjectMethod.cs).
• Session baseline: session-start/session-end events with clean-vs-crashed classification, giving session duration and crash-free-session rate.
• Usage enrichment: Analytics.SetApplicationProperty("UiFramework", "WinForms") set once at startup (forward-compatible — a future Avalonia surface sets a different value on the same property), plus duration (dwell time) added to the existing throttled SwitchToTool event.

Bug found and fixed during implementation

While writing the concurrency test for the outbox's file-claim logic, I found that System.IO.File.Move does not reliably report failure to the "losing" thread when two callers race an identical rename on .NET Framework — both can return without throwing, even though the OS performs exactly one physical rename. Verified with an isolated repro outside this codebase (~99% reproducible across hundreds of trials; confirmed via on-disk state that only one physical rename ever occurs, so the underlying filesystem operation is correct — the wrapper's exception surfacing for the loser is not). This invalidated the original "atomic rename = exclusive claim" design. Fixed by following the rename with a FileShare.None exclusive open as the real, OS-enforced single-owner check (documented as design.md D14). This was caught by AnalyticsOutboxTests.Flush_ConcurrentFlushCalls_DeliverEachEventExactlyOnce, which failed intermittently (11-20 deliveries instead of 10) before the fix, and now passes deterministically.

Test plan

• .\build.ps1 — full managed build succeeds, no native rebuild triggered.
• .\test.ps1 on FwUtilsTests — 390/390 pass, including 15 new AnalyticsOutboxTests (consent gating, FIFO delivery, cap eviction by count/age, claim-race exactly-once delivery, orphan recovery with staleness gating, delivery-failure rollback).
• .\test.ps1 on LexTextDllTests, FieldWorksTests, ITextDllTests — zero regressions from the call-site migration.
• Gap: no automated test for session-start/end tracking (FieldWorks.cs) or SwitchToTool dwell-time computation (AreaListener.cs) — both are blocked on cross-assembly access to AnalyticsOutbox's test seams (currently InternalsVisibleTo only covers FwUtilsTests). Documented as a follow-up in tasks.md §3.6/§4.6.
• Gap: no automated way to verify the UiFramework application property actually attaches to outgoing events — that's internal to the DesktopAnalytics/Mixpanel client. tasks.md §4.2.
• Manual, not yet performed: end-to-end offline queueing (disconnect network, use FieldWorks, confirm files accumulate under %LocalAppData%\SIL\FieldWorks\Analytics\Outbox\, reconnect, relaunch, confirm the directory empties). tasks.md §5.3.
• Manual, not yet performed: confirm the Tools > Options > Privacy checkbox (OkToPingBasicUsageData) still gates all telemetry, including already-queued-but-unflushed events. tasks.md §5.4.

🤖 Generated with Claude Code

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commit d0c2288d2e:
1: T1 Title exceeds max length (100>72): "Implement telemetry-migration-baseline: durable analytics outbox, session baseline, usage enrichment"

commit f92d4d0398:
1: T1 Title exceeds max length (124>72): "Propose telemetry-migration-baseline: durable analytics outbox, session baseline, and forward-compatible UI-framework marker"

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NUnit Tests

    1 files  ± 0      1 suites  ±0   10m 25s ⏱️ -14s
4 314 tests +15  4 241 ✅ +15  73 💤 ±0  0 ❌ ±0 
4 323 runs  +15  4 250 ✅ +15  73 💤 ±0  0 ❌ ±0 

Results for commit d0c2288. ± Comparison against base commit 323a022.