fix(scripting): unload compiled-script assemblies via collectible ALC

Core.Scripting-008 resolution: replace the legacy CSharpScript.CreateDelegate
path with hand-rolled CSharpCompilation + Emit + collectible AssemblyLoadContext,
so per-publish compile accretion no longer requires a server restart to reclaim.

Why this was needed:
  Roslyn's CSharpScript path emits dynamically-compiled script assemblies into
  the default AssemblyLoadContext, which is non-collectible. Across config-
  publish generations each Clear() drops dictionary entries but the emitted
  assemblies stay loaded for process lifetime, so memory grows steadily on
  long-running servers with frequent publishes. The accepted-limitation note
  in docs/VirtualTags.md recommended scheduled restarts as the workaround;
  operator feedback was that restarts are difficult, so the underlying
  limitation was the right thing to fix.

Implementation:
  - New ScriptAssemblyLoadContext(name, isCollectible: true) hosts one emitted
    script assembly per evaluator.
  - ScriptEvaluator.Compile synthesises a wrapper class around the user source
    (CompiledScript.Run(globals) — explicit return required per ordinary C#
    semantics, which every existing script already uses), builds a
    CSharpCompilation against the sandbox references, runs the
    ForbiddenTypeAnalyzer over the semantic model unchanged, emits to an
    in-memory PE stream, loads via ScriptAssemblyLoadContext.LoadFromStream,
    and binds a strongly-typed Func<ScriptGlobals<TContext>, TResult> delegate
    via reflection.
  - ScriptEvaluator now implements IDisposable — Dispose calls
    AssemblyLoadContext.Unload(), which makes the emitted assembly eligible
    for GC at the next collection cycle.
  - CompiledScriptCache.Clear() disposes every materialised evaluator before
    dropping its dictionary entry; CompiledScriptCache itself is now
    IDisposable for graceful server shutdown.
  - ScriptSandbox.Build returns a new SandboxConfig (References + Imports)
    instead of a Roslyn ScriptOptions; references now span BCL via the
    TRUSTED_PLATFORM_ASSEMBLIES set filtered to System.* + netstandard +
    Microsoft.Win32.Registry, so forbidden BCL types resolve at compile and
    ForbiddenTypeAnalyzer is the sole security gate (consistent with the
    Core.Scripting-001 / -002 model — references-list-only restriction is
    porous against type forwarding, so the analyzer must be the real gate).

Verification:
  - All 104 Core.Scripting tests pass (was 101 — three new regression tests
    locking the unload contract).
  - All 56 VirtualTags tests pass (unchanged).
  - All 63 ScriptedAlarms tests pass (unchanged).
  - New CompiledScriptCacheTests:
    - Dispose_unloads_compiled_script_assembly_load_context — proves single-
      evaluator ALC unload via WeakReference + bounded GC.Collect() loop.
    - Clear_disposes_every_materialised_evaluator — proves publish-replace
      releases every prior generation's ALC.
    - GetOrCompile_after_Dispose_throws_ObjectDisposedException — locks the
      post-dispose contract.

Docs:
  - docs/VirtualTags.md "Compile cache" section rewritten: the accepted-
    limitation note replaced with the unload contract + the new authoring
    convention (explicit return).
  - docs/ScriptedAlarms.md cross-reference updated to drop the obsolete
    restart guidance.
  - code-reviews/Core.Scripting/findings.md Core.Scripting-008 flipped
    Won't Fix → Resolved with the implementation summary.
  - code-reviews/README.md regenerated.

Pre-existing breakage note: Driver.Galaxy fails the solution-wide build on
master because its ProjectReference to the sibling mxaccessgw repo's
MxGateway.Client targets a path that the sibling repo no longer has after a
recent restructuring. This is unrelated to Core.Scripting-008 and was
verified to exist on master before this branch was cut.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

code-reviews/README.md

@@ -286,7 +286,7 @@ Findings with status `Resolved`, `Won't Fix`, or `Deferred`.
 | Core.ScriptedAlarms-011 | Low | Resolved | Code organization & conventions | `Part9StateMachine.cs:275` |
 | Core.Scripting-005 | Low | Resolved | Correctness & logic bugs | `DependencyExtractor.cs:97` |
 | Core.Scripting-006 | Low | Resolved | Concurrency & thread safety | `CompiledScriptCache.cs:55` |
-| Core.Scripting-008 | Low | Won't Fix | Performance & resource management | `CompiledScriptCache.cs:34`, `ScriptEvaluator.cs:34` |
+| Core.Scripting-008 | Low | Resolved | Performance & resource management | `CompiledScriptCache.cs:34`, `ScriptEvaluator.cs:34` |
 | Core.Scripting-009 | Low | Resolved | Design-document adherence | `ForbiddenTypeAnalyzer.cs:45` |
 | Core.Scripting-011 | Low | Resolved | Testing coverage | `tests/Core/ZB.MOM.WW.OtOpcUa.Core.Scripting.Tests/` |
 | Core.VirtualTags-004 | Low | Resolved | Correctness & logic bugs | `src/Core/ZB.MOM.WW.OtOpcUa.Core.VirtualTags/VirtualTagEngine.cs:349` |