Stop versioning DI and ISA95 packages as preview (#4686)

## Summary
Removes the **DI** (`Opc.Ua.Di*`) and **ISA95** (`Opc.Ua.ISA95*`)
package families from the preview-only set, so they ship with the stable
root version (e.g. `2.0.1` instead of `2.0.1-preview.N`).

- `version.targets`: drop the two `_IsPreviewPackage` conditions.
- `.azurepipelines/package-version-policy.ps1`: drop `ISA95|Di` from
`Test-PreviewPackageId`. It must match `version.targets`, because the
package-set validator fails if the two disagree.
- `PackageVersionPolicyTests`: ISA95/Di IDs are now expected to be
non-preview, they are removed from the classifier-agreement token list,
and the "already-preview base version" case now uses Robotics.
- Docs (`DeveloperGuide.md`, `ReleaseProcess.md`, `docs/README.md`): the
preview-family list no longer includes DI or ISA95, and the "preview
package" label is removed from the DI, Software Update (part of the DI
packages), and ISA-95 entries.

## Test
`dotnet test tests/Opc.Ua.Tools.Tests --filter PackageVersionPolicy`
(net10.0): 87/87 passed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

docs/DeveloperGuide.md

@@ -380,7 +380,7 @@ From **2.0** onward, package versions are produced by [Nerdbank.GitVersioning](h
 Stable (public-release) versions are produced **only** from a canonical `release/<major>.<minor>` branch (e.g. `release/2.0`, `release/2.1`) — never from `master`, a tag, or any other branch — and only at the exact commit whose `version.json` carries the plain `<major>.<minor>.<patch>` version with no prerelease label (e.g. `2.0.0`). Patch numbers increase by exactly one per release on their line (`2.0.0` → `2.0.1` → `2.0.2`); a new minor line resets the patch to zero (`2.1.0`). See **[Release process](ReleaseProcess.md)** for the full branch/version model and the step-by-step procedure for cutting a release, shipping a patch or minor version, backporting a fix, and promoting a stable candidate.
 
 The XRegistry, WoT Connectivity, Vision, Robotics, Redundancy, Positioning,
-OpenUSD, ISA95, AI, and DI package families remain preview packages even when
+OpenUSD, and AI package families remain preview packages even when
 the root version is stable. Their numeric version follows the root version:
 for example, a stable `2.0.0` root produces `2.0.0-preview.N` for these
 families (`N` a committed, manually curated number in `preview-version.props`