Migrate playground from CheerpJ to TeaVM

[CommanderTvis]

Summary

• Drop CheerpJ; compile the rell3 bridge to JS ahead-of-time with TeaVM 0.12.0
• Replace Bun with com.github.node-gradle.node + pnpm 10.20.0 + Vite 8 (Monaco loads via ?worker query imports)
• Switch the Rell coordinate to 0.16.0-SNAPSHOT (resolved from the official GitLab Maven repo)
• Add a TeaVM ClassHolderTransformer plugin (MissingMethodInjector) that grafts ~140 missing JDK methods/fields onto teavm-classlib classes, replaces JVM-only method bodies (e.g. Rt_RellVersion.getBuildProperties) with silent stubs at compile time, and wires an SLF4J no-op shim through the T-prefix renamer
• Add a Vitest-based "Rell survival kit" (39 tests) under :web:vitestRun that loads the TeaVM bridge JS and exercises arithmetic, strings, control flow, functions, collections, structs/enums, nullables, stdlib, error surfaces, and REPL session continuity
• Fix REPL init flake: retry ReplInterpreter.create() up to three times in both ReplSession and ModuleSession (the first JVM-in-JS touch of jOOQ/Jackson/kotlin-reflect static-init throws non-deterministically per worker) and surface the captured channel events instead of an opaque repl:not_ready

Test plan

• ./gradlew :bridge:generateJavaScript :bridge:copyTeavmToWeb produces web/public/teavm/rell-playground-bridge.js
• ./gradlew :web:vitestRun — 39/39 green against the GitLab snapshot
• ./gradlew :web:viteDev and click Run in Chrome — verify first-click no longer hits repl:not_ready and that print(...) round-trips

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