Add ProfileMigration version-migration coverage tests

[anagnorisis2peripeteia]

A follow-up to #37. ProfileMigration upgrades old controller-profile XML to the current format (config_version 5) through a chain of steps, but only two tests cover it — and one of those (CheckJaysProfileRead) is excluded from CI for snapshot fragility — so the per-step migration logic is largely unasserted.

This adds six tests that assert migration behaviour with targeted attribute/element checks (deliberately not full-document string diffs, which is what got the existing test excluded):

• RequiresMigration for old (config_version=1), absent, and current (=5) profiles.
• After Migrate(), config_version reaches the current version and UsedMigration is set — and stays false for an already-current profile.
• Version0002: a non-positive LSDeadZone is normalized to the default deadzone; a positive value passes through.
• Version0004: legacy GyroSmoothing* nodes become the GyroMouseSmoothingSettings / GyroMouseStickSmoothingSettings groups (with the conditional SmoothingMethod).
• Version0005: UseTPforControls remaps to TouchpadOutputMode.
• DetermineProfileVersion: a version-absent profile containing LSAntiDeadZone is detected as v2 (its LSDeadZone is preserved, not v1-normalized).

Test-only; no behaviour change.

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_{Local review history: https://gist.github.com/fc75801ef643a30731c2b87394c3a935}

Proof manifest

Before / After (same command, same machine)

dotnet test DS4WindowsTests\DS4WindowsTests.csproj -c Release -p:Platform=x64 --filter "Name!=CheckSettingsSave&Name!=CheckWriteProfile&Name!=CheckJaysProfileRead&Name!=CheckSettingsRead"

Run	Result
Base + injected fault (Version0005 writes Mouse instead of Controls)	✅ suite passes — fault missed (the coverage gap)
This branch + the same fault	❌ Migrate_TransformsVersion0005_UseTPforControls fails — fault caught
This branch, clean	✅ suite passes

Fault-injection proof (test-only PR): made Version0005 write TouchpadOutMode.Mouse instead of Controls, identically on base and this branch. Base + fault: suite passes (fault missed). This branch + fault: Migrate_TransformsVersion0005_UseTPforControls fails (fault caught). Clean branch: suite passes. Mutation delta on ProfileMigration.cs: 28.0% -> 59.2%, posted above.

Manifest + raw run outputs: https://gist.github.com/anagnorisis2peripeteia/f78f8b91812cb8d3b6009be38c42b2df

[anagnorisis2peripeteia]

Before/after behavioral evidence — mutation testing (Stryker.NET) of ProfileMigration.cs:

	Killed	Survived	No coverage	Score
Before (existing tests only)	37	95	57	28.0%
After (with these six tests)	100	69	8	59.2%

The new tests kill 63 previously-surviving mutants and drop no-coverage mutants from 57 to 8 — the per-step migration logic (Version0002/0004/0005, DetermineProfileVersion) that previously had no behavioural assertions. Measured on **/ProfileMigration.cs, both runs on the same base.