fix(lint): resolve noUnusedLocals regression in MainAgent.classify_via_llm

R4 introduced classify_via_llm() which built classification_prompt but
fell through to regex without using it, tripping noUnusedLocals (TS6133).
Use 'void classification_prompt' to preserve the GA prompt structure as
documentation while satisfying strict lint. Removed console.warn (no
@types/node / dom lib in ES2022 target).

Regression scope: third-round verification.
- 169/169 tests pass
- IPC files (B14) bun-build clean (EXIT=0)
- MainAgent transpile clean (EXIT=0)
- Confirmed remaining tsc errors are environmental (missing @types/node:
  fs/path/crypto/Buffer) or pre-existing (config write-only field,
  EventIngestor value-as-type), NOT R4 regressions.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/runtime/src/agents/main/MainAgent.ts

@@ -133,8 +133,8 @@ export class MainAgent {
     try {
       // GA: const result = await this.provider_manager.complete(classification_prompt, ...)
       // GA: return parse_classification(result.content)
-      // For now, fall through to regex as a safety net
+      // Alpha: prompt is built but not yet sent; fall through to regex as a safety net.
-      console.warn('[MainAgent] LLM classify not yet wired (GA); falling back to regex')
+      void classification_prompt
       return this.classify_regex(message)
     } catch {
       return this.classify_regex(message)