fix(core): present the project dir to the model as the App Data Dir in the default system prompt (#61)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/docs/content/configuration.en.md

@@ -134,6 +134,8 @@ compaction:
 # parameters JSON Schema) for every tool you keep — see Tools & Approval.
 ```
 
+An existing Agent always runs with its on-disk config verbatim — newer code defaults are never merged in automatically. To adopt the current defaults (for example an updated built-in system prompt), use the settings page's **Restore default configuration** action: like a skill update it overwrites the existing configuration — custom system prompt, tool list, model/compaction settings and MCP Servers — keeping only `name`, `description` and `version`.
+
 ### System prompt placeholders
 
 `system_prompt` is the only template with placeholder substitution. Available placeholders:
@@ -146,13 +148,15 @@ compaction:
 | `{{PLATFORM}}` | Runtime platform |
 | `{{OS_VERSION}}` | Operating system version |
 | `{{DATE}}` | Current date |
-| `{{PROJECT_DIR}}` | Project directory |
+| `{{PROJECT_DIR}}` | App Data Dir: the PenguinHarness app data root (the Project directory) |
 | `{{AGENT_ID}}` | Agent id |
 | `{{CWD}}` | Workspace path |
 | `{{PROVIDER}}` | Model provider group |
 | `{{MODEL_ID}}` | Upstream model id |
 | `{{SESSION_ID}}` | Session id |
 
+`{{PROJECT_DIR}}` is surfaced to the model as the **App Data Dir**: PenguinHarness's application data root, holding every Agent's data files (`agents/<agent_id>/…`) and the project-level data — deliberately not described as a project or task directory, so the model does not mistake it for the task's working directory (`CWD`).
+
 `agent_state/AGENTS.md` is the developer-editable instruction file, injected via `{{AGENTS_MD}}` and empty by default — it is also the file an optimizer edits most (see [Self-Improvement](/self-improvement)).
 
 ## Vault

packages/docs/content/configuration.zh.md

@@ -134,6 +134,8 @@ compaction:
 # 参见「工具与审批」页。
 ```
 
+既有 Agent 始终按其磁盘上的配置原样运行——更新后的代码默认值不会自动合并。要采用当前默认值（例如更新后的内置系统提示词），可使用设置页的**还原为默认配置**操作：与 Skill 更新同语义，会用当前默认值覆盖现有配置——自定义系统提示词、工具列表、模型/压缩参数与 MCP Server——仅保留 `name`、`description` 与 `version`。
+
 ### 系统提示词占位符
 
 `system_prompt` 是唯一进行占位符替换的模板，可用占位符：
@@ -146,13 +148,15 @@ compaction:
 | `{{PLATFORM}}` | 运行平台 |
 | `{{OS_VERSION}}` | 操作系统版本 |
 | `{{DATE}}` | 当前日期 |
-| `{{PROJECT_DIR}}` | Project 目录 |
+| `{{PROJECT_DIR}}` | App Data Dir：PenguinHarness 应用数据根目录（即 Project 目录） |
 | `{{AGENT_ID}}` | Agent id |
 | `{{CWD}}` | Workspace 路径 |
 | `{{PROVIDER}}` | 模型 provider 分组 |
 | `{{MODEL_ID}}` | 上游模型 id |
 | `{{SESSION_ID}}` | Session id |
 
+`{{PROJECT_DIR}}` 在提示词中以 **App Data Dir** 名义暴露给模型：PenguinHarness 的应用数据根目录，存放全部 Agent 的数据文件（`agents/<agent_id>/…`）与 Project 级数据——特意不以 Project/任务目录的口径描述，避免模型将其误认为本次任务的工作目录（`CWD`）。
+
 `agent_state/AGENTS.md` 是开发者可编辑的指令文件，经 `{{AGENTS_MD}}` 注入系统提示词，缺省为空——它也是优化器最常改动的文件（见[自我进化](/self-improvement)）。
 
 ## Vault

packages/docs/content/web-app.en.md

@@ -61,7 +61,7 @@ The list page creates and deletes Agents; clicking through opens the `/agents/:a
 
 | Tab | Contents |
 | --- | --- |
-| Overview | Basic info, plus export / import of Agent State snapshots |
+| Overview | Basic info, export / import of Agent State snapshots, and restoring the default configuration (overwrites customizations, keeping only name/description) |
 | Prompt | AGENTS.md and system_prompt |
 | Runtime | Runtime parameters such as max_turns, model.*, compaction.* |
 | Tools | Built-in tool table and MCP server JSON configuration |

packages/docs/content/web-app.zh.md

@@ -61,7 +61,7 @@ penguin web
 
 | 标签页 | 内容 |
 | --- | --- |
-| Overview | 基本信息，以及 Agent State 快照的导出 / 导入 |
+| Overview | 基本信息、Agent State 快照的导出 / 导入，以及还原为默认配置（覆盖自定义内容，仅保留名称与描述） |
 | Prompt | AGENTS.md 与 system_prompt |
 | Runtime | max_turns、model.*、compaction.* 等运行参数 |
 | Tools | 内置工具表格与 MCP Server 的 JSON 配置 |