fix(config): enable compact_context by default (#3995)

* fix: change compact_context default to true

Local LLMs with limited context windows immediately run out of context
when compact_context defaults to false. The system prompt alone can
consume 25K+ tokens, exceeding even 55K context windows with history.

Setting compact_context=true by default limits system prompt injection
to 6000 chars and RAG results to 2 chunks, making the agent usable
with smaller models out of the box.

Fixes #3987

* docs: update compact_context default to true in config reference

Update all locale variants (en, zh-CN, vi) to reflect the new default.

* test: update tests to expect compact_context default of true

Update assertions in schema.rs unit tests and config_persistence.rs
component tests to match the new default value.

docs/i18n/zh-CN/reference/api/config-reference.zh-CN.md

@@ -76,7 +76,7 @@ runtime_trace_max_entries = 200
 
 | 键 | 默认值 | 用途 |
 |---|---|---|
-| `compact_context` | `false` | 为 true 时：bootstrap_max_chars=6000，rag_chunk_limit=2。适用于 13B 或更小的模型 |
+| `compact_context` | `true` | 为 true 时：bootstrap_max_chars=6000，rag_chunk_limit=2。适用于 13B 或更小的模型 |
 | `max_tool_iterations` | `10` | 跨 CLI、网关和渠道的每条用户消息的最大工具调用循环轮次 |
 | `max_history_messages` | `50` | 每个会话保留的最大对话历史消息数 |
 | `parallel_tools` | `false` | 在单次迭代中启用并行工具执行 |

docs/reference/api/config-reference.md

@@ -76,7 +76,7 @@ Operational note for container users:
 
 | Key | Default | Purpose |
 |---|---|---|
-| `compact_context` | `false` | When true: bootstrap_max_chars=6000, rag_chunk_limit=2. Use for 13B or smaller models |
+| `compact_context` | `true` | When true: bootstrap_max_chars=6000, rag_chunk_limit=2. Use for 13B or smaller models |
 | `max_tool_iterations` | `10` | Maximum tool-call loop turns per user message across CLI, gateway, and channels |
 | `max_history_messages` | `50` | Maximum conversation history messages retained per session |
 | `parallel_tools` | `false` | Enable parallel tool execution within a single iteration |

docs/vi/config-reference.md

@@ -65,7 +65,7 @@ Lưu ý cho người dùng container:
 
 | Khóa | Mặc định | Mục đích |
 |---|---|---|
-| `compact_context` | `false` | Khi bật: bootstrap_max_chars=6000, rag_chunk_limit=2. Dùng cho model 13B trở xuống |
+| `compact_context` | `true` | Khi bật: bootstrap_max_chars=6000, rag_chunk_limit=2. Dùng cho model 13B trở xuống |
 | `max_tool_iterations` | `10` | Số vòng lặp tool-call tối đa mỗi tin nhắn trên CLI, gateway và channels |
 | `max_history_messages` | `50` | Số tin nhắn lịch sử tối đa giữ lại mỗi phiên |
 | `parallel_tools` | `false` | Bật thực thi tool song song trong một lượt |

src/config/schema.rs

@@ -1141,7 +1141,7 @@ fn default_agent_tool_dispatcher() -> String {
 impl Default for AgentConfig {
     fn default() -> Self {
         Self {
-            compact_context: false,
+            compact_context: true,
             max_tool_iterations: default_agent_max_tool_iterations(),
             max_history_messages: default_agent_max_history_messages(),
             max_context_tokens: default_agent_max_context_tokens(),
@@ -8828,7 +8828,7 @@ reasoning_effort = "turbo"
     #[test]
     async fn agent_config_defaults() {
         let cfg = AgentConfig::default();
-        assert!(!cfg.compact_context);
+        assert!(cfg.compact_context);
         assert_eq!(cfg.max_tool_iterations, 10);
         assert_eq!(cfg.max_history_messages, 50);
         assert!(!cfg.parallel_tools);

tests/component/config_persistence.rs

@@ -72,11 +72,11 @@ fn agent_config_default_tool_dispatcher() {
 }
 
 #[test]
-fn agent_config_default_compact_context_off() {
+fn agent_config_default_compact_context_on() {
     let agent = AgentConfig::default();
     assert!(
-        !agent.compact_context,
-        "compact_context should default to false"
+        agent.compact_context,
+        "compact_context should default to true"
     );
 }
 
@@ -204,7 +204,7 @@ default_temperature = 0.7
     // Agent config should use defaults
     assert_eq!(parsed.agent.max_tool_iterations, 10);
     assert_eq!(parsed.agent.max_history_messages, 50);
-    assert!(!parsed.agent.compact_context);
+    assert!(parsed.agent.compact_context);
 }
 
 #[test]