cleanup: drop dead ReScript/TS duplicates; LSP via affinescript server

Part of task #8 (reduce the banned-language footprint):
- Delete playground/compiler/* (a dead, unwired duplicate mini-compiler;
  imported nowhere). NOTE it carried a unique ErrorInjector.res — flagged in
  case the educational error-injection demo should be re-introduced later.
- Delete bench/BenchLexer.res + bench/BenchParser.res (unreferenced benchmarks).
- Delete cli/lsp-server.ts (274-line TypeScript LSP) — superseded by the
  compiler's built-in `affinescript server` (JSON-RPC LSP on stdin/stdout);
  README.adoc updated to invoke it.

Compiler/src .affine harness still green (unaffected).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0195yA45jSSP7YDPwJSpw4bM

Author: hyperpolymath

README.adoc

@@ -233,8 +233,8 @@ deno run -A cli/visual-feedback.js program.err
 
 [source,bash]
 ----
-# Start LSP server for IDE integration
-deno run --allow-all cli/lsp-server.ts
+# Start LSP server for IDE integration (built into the AffineScript compiler)
+affinescript server
 ----
 
 Features: