perf(agent): rombak alur AI agent — adaptif, hemat token, self-healing

Ganti explore phase MANDATORY (3 subagent tiap turn, boros) dengan
tool explore_codebase yang DIPUTUSKAN agent sendiri (lazy, token-aware):
- hapus ExploreService trait + with_explore + Phase 0 dari turn loop
- ExploreServiceImpl kini jadi tool 'explore_codebase' (1 context-scout
  subagent, read-only, cap output 4k chars)
- system prompt: instruksi TOKEN BUDGET (jawab langsung utk query simple,
  panggil explore_codebase sekali utk task kompleks)

Loop utama kini adaptif & self-healing:
- max_tokens adaptif (800/1600/4096 by request length) — bukan selalu 4096
- temperature 0.2 saat tool-calling, 0.7 utk final answer
- ErrorTracker: deteksi tool error berulang → inject recovery note,
  stop setelah 8 error total (bukan 50 iterasi sia-sia)
- auto-compact history > 60k chars sebelum LLM call
- tool output di-truncate ke 12k chars sebelum masuk konteks

Tambah 8 unit test (truncation, adaptive tokens, error tracker).

apps/application/src/lib.rs

@@ -52,5 +52,5 @@ pub use cms::{
 
 pub use agent::{
     turn_service::{compact_messages_with_ai, AgentTurnServiceImpl},
-    AgentTurnService, ExploreOutput, ExploreService, ToolExecutor,
+    AgentTurnService, ToolExecutor,
 };