feat(core): support QWEN_HOME env var to customize config directory

docs/users/configuration/settings.md

@@ -570,6 +570,8 @@ For authentication-related variables (like `OPENAI_*`) and the recommended `.qwe
 
 | Variable                                           | Description                                                                                                                                                                                                                                                                       | Notes                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
 | -------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `QWEN_HOME`                                        | Customizes the global configuration directory (default: `~/.qwen`). Accepts an absolute or relative path (relative paths are resolved from the current working directory). Leading `~` is expanded to the user's home directory.                                                  | Stores credentials, settings, memory, skills, and other global state. When set, project-level `.qwen/` directories are unaffected. An empty string is treated as unset.                                                                                                                                                                                                                                                                                                            |
+| `QWEN_RUNTIME_DIR`                                 | Overrides the runtime output directory (conversations, logs, todos). When unset, defaults to the `QWEN_HOME` directory.                                                                                                                                                           | Use this to separate ephemeral runtime data from persistent config. Useful when `QWEN_HOME` is on a shared/slow filesystem.                                                                                                                                                                                                                                                                                                                                                        |
 | `QWEN_TELEMETRY_ENABLED`                           | Set to `true` or `1` to enable telemetry. Any other value is treated as disabling it.                                                                                                                                                                                             | Overrides the `telemetry.enabled` setting.                                                                                                                                                                                                                                                                                                                                                                                                                                         |
 | `QWEN_TELEMETRY_TARGET`                            | Sets the telemetry target (`local` or `gcp`).                                                                                                                                                                                                                                     | Overrides the `telemetry.target` setting.                                                                                                                                                                                                                                                                                                                                                                                                                                          |
 | `QWEN_TELEMETRY_OTLP_ENDPOINT`                     | Sets the OTLP endpoint for telemetry.                                                                                                                                                                                                                                             | Overrides the `telemetry.otlpEndpoint` setting.                                                                                                                                                                                                                                                                                                                                                                                                                                    |
@@ -589,6 +591,10 @@ For authentication-related variables (like `OPENAI_*`) and the recommended `.qwe
 | `QWEN_CODE_UNATTENDED_RETRY`                       | Set to `true` or `1` to enable persistent retry mode. When enabled, transient API capacity errors (HTTP 429 Rate Limit and 529 Overloaded) are retried indefinitely with exponential backoff (capped at 5 minutes per retry) and heartbeat keepalives every 30 seconds on stderr. | Designed for CI/CD pipelines and background automation where long-running tasks should survive temporary API outages. Must be set explicitly — `CI=true` alone does **not** activate this mode. See [Headless Mode](../features/headless#persistent-retry-mode) for details. Example: `export QWEN_CODE_UNATTENDED_RETRY=1`                                                                                                                                                        |
 | `QWEN_CODE_PROFILE_STARTUP`                        | Set to `1` to enable startup performance profiling. Writes a JSON timing report to `~/.qwen/startup-perf/` with per-phase durations.                                                                                                                                              | Only active inside the sandbox child process. Zero overhead when not set. Example: `export QWEN_CODE_PROFILE_STARTUP=1`                                                                                                                                                                                                                                                                                                                                                            |
 
+When both user-level `.env` files define the same variable, the Qwen-specific
+file wins: `<QWEN_HOME>/.env` (or `~/.qwen/.env` when `QWEN_HOME` is unset) is
+loaded before `~/.env`, and existing environment values are not overwritten.
+
 ## Command-Line Arguments
 
 Arguments passed directly when running the CLI can override other configurations for that specific session.