fix(code-review): resolve Batch 2 open findings (AbCip, AbLegacy, Galaxy, FOCAS)

- Driver.AbCip.Contracts-001: parse 'writable' from TagConfig JSON (default true) instead of hardcoding
- Driver.AbCip.Contracts-002/-003: Dt type comment; drop dead [Display]/[Range] annotations
- Driver.AbCip.Contracts-004: dedicated AbCipEquipmentTagParser test class (+15)
- Driver.AbCip-017: document Tick severity Low-fallback on Bad severity read
- Driver.AbLegacy.Contracts-002/-003/-004: isArray-scalar remarks (+tests), MaxTagBytes/ForFamily docs
- Driver.Galaxy.Browser-003 + Driver.Galaxy.Contracts-003: extract ResolveApiKey -> GalaxySecretRef (dedup)
- Driver.Galaxy-019: cache buffered-interval only on Ok + ILogger warnings + ClassifyIntervalReply (+tests)
- Driver.FOCAS.Contracts-002: thread WriteIdempotent through DiscoverAsync (+test)

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Contracts/GalaxyDriverOptions.cs

@@ -30,7 +30,7 @@ public sealed record GalaxyDriverOptions(
 
 /// <summary>
 ///     Connection details for the MxAccess gateway. <see cref="ApiKeySecretRef"/> is
-///     resolved by <c>GalaxyDriver.ResolveApiKey</c> at InitializeAsync time. Four forms
+///     resolved by <see cref="GalaxySecretRef.ResolveApiKey"/> at InitializeAsync time. Four forms
 ///     supported, in priority order:
 ///     <list type="bullet">
 ///       <item><c>env:NAME</c> — read from an environment variable (recommended for