Debugger (#1410)

* Add debugger backend.

This adds on a debugger to the evaluation loop, that allows for pausing,
saving state, then resuming from saved state.

* DAP debug server, multi-thread debugging, and iterative interpreter debug support

   - Add MSDebugServer implementing the Debug Adapter Protocol over TCP,
     with launch/attach modes, breakpoints, step-over/step-in/step-out,
     variable inspection, exception breakpoints, and watch expressions
   - Add multi-thread DAP support: register/unregister threads, per-thread
     pause states, sync and async stepping modes (sync blocks in place,
     async snapshots state and resumes on a new thread)
   - Refactor DebugContext into a full thread-aware debug state manager with
     per-thread StepMode, ThreadDebugState, and a thread registry for DAP
   - Add DaemonManager lifecycle listeners and thread-aware waitForThreads,
     so the debug session stays alive while background threads run
   - Extract spawnExecutionThread() to centralize execution thread lifecycle
     (run, await daemons, signal completion) in one place
   - Fix StackTraceManager thread affinity: remove isDebugAdopted flag so
     background threads (x_new_thread) get their own STM instead of sharing
     the main thread's, which was corrupting call depth for step-over
   - Fix skippingResume flag: clear unconditionally on source line change
     rather than requiring shouldStop=true, which blocked step-over returns
   - Add StackTraceFrame.getTarget() for debugger source mapping
   - Add Breakpoint condition/hitCount/logMessage support
   - Wire up cmdline interpreter (--debug flag) and lang server for DAP
   - Add DAPTestHarness and dual sync/async integration tests for step-over
     and multi-thread step-over scenarios
   - Add debugger dependency (lsp4j.debug) to pom.xml

* Add logpoint support

* Add attach mode and KEYPAIR security

* Add docs and final touches

* Debug infrastructure: managed mode, hit-count dedup, and comprehensive tests

 - Enable managed execution mode in CommandHelperPlugin so the debug
   session survives script completion on embedded (Minecraft) servers
 - Fix hit-count breakpoint deduplication: multiple AST nodes on the same
   source line no longer increment the hit counter more than once per
   visit. Uses column-based caching in ThreadDebugState to distinguish
   "same line, different node" from "new loop iteration, same first node"
 - Add evaluateBreakpointCondition() to DebugContext with per-thread
   cache-aware hit-count and condition evaluation
 - Add Breakpoint.getHitCount() getter
 - Add MSDebugServer managed mode support: setManagedExecution(),
   startedOnHostMainThread capture, resumeOnHostMainThread() for
   resuming on the server main thread, dynamic scripting mode flag
   in evaluate handler
 - Add 21 new DAP integration tests (39 total) covering: managed mode
   step-over, thread events, disconnect; variables/scopes; CArray
   expansion (indexed, associative, nested); evaluate expressions;
   exception breakpoints; conditional and hit-count breakpoints;
   step-in, step-out, step-in targets; disconnect resumes execution

* Fix flakey test

Author: LadyCailin

pom.xml

@@ -133,8 +133,8 @@
 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<maven.test.failure.ignore>true</maven.test.failure.ignore>
-		<maven.compiler.source>16</maven.compiler.source>
-		<maven.compiler.target>16</maven.compiler.target>
+		<maven.compiler.source>21</maven.compiler.source>
+		<maven.compiler.target>21</maven.compiler.target>
 	</properties>
 	<repositories>
 		<repository>
@@ -376,6 +376,11 @@
 			<artifactId>org.eclipse.lsp4j</artifactId>
 			<version>0.22.0</version>
 		</dependency>
+		<dependency>
+			<groupId>org.eclipse.lsp4j</groupId>
+			<artifactId>org.eclipse.lsp4j.debug</artifactId>
+			<version>0.22.0</version>
+		</dependency>
 		<dependency>
 			<groupId>io.swagger.core.v3</groupId>
 			<artifactId>swagger-annotations</artifactId>
@@ -489,7 +494,7 @@
 				<version>3.12.1</version>
 				<configuration>
 					<showDeprecation>true</showDeprecation>
-					<release>16</release>
+					<release>21</release>
 					<compilerArgs>
 						<arg>-XDignore.symbol.file</arg>
 						<arg>-parameters</arg>
@@ -569,6 +574,8 @@
 									<include>org.brotli:dec:jar:*</include>
 									<include>org.eclipse.lsp4j:org.eclipse.lsp4j:jar:*</include>
 									<include>org.eclipse.lsp4j:org.eclipse.lsp4j.jsonrpc:jar:*</include>
+									<include>org.eclipse.lsp4j:org.eclipse.lsp4j.debug:jar:*</include>
+									<include>org.eclipse.lsp4j:org.eclipse.lsp4j.jsonrpc.debug:jar:*</include>
 									<!-- We don't currently actually depend on these 2, but lsp4j does, so we
 									need to shade it in. In the future, we may rip out org.json:json,
 									and replace it with this, however, in which case we only need to
@@ -842,6 +849,24 @@
 										<exclude>META-INF/**</exclude>
 									</excludes>
 								</filter>
+								<filter>
+									<artifact>org.eclipse.lsp4j:org.eclipse.lsp4j.debug:jar:*</artifact>
+									<includes>
+										<include>**</include>
+									</includes>
+									<excludes>
+										<exclude>META-INF/**</exclude>
+									</excludes>
+								</filter>
+								<filter>
+									<artifact>org.eclipse.lsp4j:org.eclipse.lsp4j.jsonrpc.debug:jar:*</artifact>
+									<includes>
+										<include>**</include>
+									</includes>
+									<excludes>
+										<exclude>META-INF/**</exclude>
+									</excludes>
+								</filter>
 								<filter>
 									<artifact>com.google.code.gson:gson:jar:*</artifact>
 									<includes>