fix(scripting): stop unbounded script recursion from killing the server (lmxopcua#779)

Reproduced first, out of process (ScriptRecursionContainmentTests re-launches
the xunit v3 test assembly to run one recursive script through
ScriptEvaluator + ScriptRunGuard, so the runner never executes one): before
this change every shape — local function, mutual local functions,
self-referencing Func<>, anonymous self-application, recursion through LINQ,
an expression-bodied void lambda, an anonymous method — ended the child with
exit 134 (SIGABRT, "Stack overflow."). A StackOverflowException cannot be
caught, so in production one script takes the whole node down.

Fix: ScriptEvaluator.Compile now rewrites the validated wrapper
(ScriptStackGuardInjector, after ForbiddenTypeAnalyzer) so the script body and
every lambda, anonymous method and local function starts with
ScriptStackGuard.Check(), which throws ScriptStackExhaustedException when
RuntimeHelpers.TryEnsureSufficientExecutionStack reports the stack nearly
spent. The script then fails like any throwing script (Bad, script log) and
the process lives.

Why a runtime check, not an analyzer rule: recursion is not decidable from
syntax (anonymous self-application never names itself), and bounded recursion
must keep working. Expression-bodied lambdas/local functions become blocks
(`return e;` or `e;`, chosen from the bound symbol, so the same overload
binds); expression-tree and async lambdas are left alone. Limits (documented
on ScriptStackGuard and in docs/VirtualTags.md): depth depends on the thread's
stack size; a recursion that never re-enters script code is not seen; a script
may catch the exception, which only unwinds it.

Tests: ScriptRecursionContainmentTests (7 shapes, child process each; all 7
fail with exit 134 when the rewrite is disabled), ScriptStackGuardInjectionTests
(bounded recursion and every rewritten lambda/local-function shape keep their
value; the expression-tree case fails if those lambdas are rewritten).

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

docs/plans/2026-11-09-out-of-process-script-runner-design.md

@@ -88,7 +88,7 @@ used only by single-shot callers (`:18-27`).
 |---|---|---|
 | `while(true){}` (ignores the token) | The pool thread spins **forever**, holding one core and its collectible ALC. The guard bounds this to one orphan per key and then quarantines, but the thread keeps spinning until the process restarts. N such scripts peg N cores. | `ScriptRunGuard.cs:17-22` remarks; `ScriptRunGuardTests.cs:170-205` asserts *exactly one* orphan stays in flight (`InFlightCount.ShouldBe(1)`) |
 | Fast allocation (`new byte[int.MaxValue]` in a loop, or a growing list) | The sample is taken **after** the delegate returns, so the process can OOM first. The whole server dies, including OPC UA sessions and every driver. | `ScriptRunGuard.cs:39-43`; `docs/VirtualTags.md:40`; review `docs/reviews/2026-10-21/05-core.md:100-105` |
-| Unbounded recursion (a local function or a self-referencing `Func<>`; neither is a class member, so `EnforceSingleRunMember` does not see it) | `StackOverflowException` cannot be caught in .NET and **terminates the host process**. **[A-1]** I did not reproduce this; it follows from runtime semantics, and no analyzer rule targets recursion (`git grep -i "recursion\|StackOverflow"` in `Core.Scripting` finds nothing). | `ScriptEvaluator.cs:228-281` (member check only) |
+| Unbounded recursion (a local function or a self-referencing `Func<>`; neither is a class member, so `EnforceSingleRunMember` does not see it) | `StackOverflowException` cannot be caught in .NET and **terminates the host process**. **[A-1]** I did not reproduce this; it follows from runtime semantics, and no analyzer rule targets recursion (`git grep -i "recursion\|StackOverflow"` in `Core.Scripting` finds nothing). **Update (lmxopcua#779):** reproduced out of process (exit 134, "Stack overflow.") and fixed in-process: the compile injects `ScriptStackGuard.Check()` into every script body, so the script now fails with a catchable `ScriptStackExhaustedException`. | `ScriptEvaluator.cs:228-281` (member check only) |
 | Collectible-ALC reclaim of a stuck script | `ClearCompiledScripts` disposes the evaluator, but an ALC cannot be collected while a thread is executing its code, so a stuck orphan pins its assembly until restart. **[A-2]** This is .NET ALC semantics, not observed here. | `CompiledScriptCache.Clear`; `ScriptEvaluator.Dispose` |
 | A slow (not runaway) script | VT: blocks a default-dispatcher thread for up to 2 s per evaluation. Calc / alarm: holds the driver-wide or engine-wide gate, so every sibling waits behind it (up to 2 s / 250 ms each). | `RoslynVirtualTagEvaluator.cs:174-175`; `CalculationDriver.cs:539-541`; `ScriptedAlarmEngine.cs:743-765` |