Fixed: #2034

feat(proxy): centralize proxy handling with `proxyutil` package and enhance test coverage

- Added `proxyutil` package to simplify proxy handling across the codebase.
- Refactored various components (`executor`, `cliproxy`, `auth`, etc.) to use `proxyutil` for consistent and reusable proxy logic.
- Introduced support for "direct" proxy mode to explicitly bypass all proxies.
- Updated tests to validate proxy behavior (e.g., `direct`, HTTP/HTTPS, and SOCKS5).
- Enhanced YAML configuration documentation for proxy options.

config.example.yaml

@@ -63,6 +63,7 @@ error-logs-max-files: 10
 usage-statistics-enabled: false
 
 # Proxy URL. Supports socks5/http/https protocols. Example: socks5://user:pass@192.168.1.1:1080/
+# Per-entry proxy-url also supports "direct" or "none" to bypass both the global proxy-url and environment proxies explicitly.
 proxy-url: ""
 
 # When true, unprefixed model requests only use credentials without a prefix (except when prefix == model name).
@@ -110,6 +111,7 @@ nonstream-keepalive-interval: 0
 #     headers:
 #       X-Custom-Header: "custom-value"
 #     proxy-url: "socks5://proxy.example.com:1080"
+#     # proxy-url: "direct" # optional: explicit direct connect for this credential
 #     models:
 #       - name: "gemini-2.5-flash" # upstream model name
 #         alias: "gemini-flash"    # client alias mapped to the upstream model
@@ -128,6 +130,7 @@ nonstream-keepalive-interval: 0
 #     headers:
 #       X-Custom-Header: "custom-value"
 #     proxy-url: "socks5://proxy.example.com:1080" # optional: per-key proxy override
+#     # proxy-url: "direct" # optional: explicit direct connect for this credential
 #     models:
 #       - name: "gpt-5-codex"   # upstream model name
 #         alias: "codex-latest" # client alias mapped to the upstream model
@@ -146,6 +149,7 @@ nonstream-keepalive-interval: 0
 #     headers:
 #       X-Custom-Header: "custom-value"
 #     proxy-url: "socks5://proxy.example.com:1080" # optional: per-key proxy override
+#     # proxy-url: "direct" # optional: explicit direct connect for this credential
 #     models:
 #       - name: "claude-3-5-sonnet-20241022" # upstream model name
 #         alias: "claude-sonnet-latest"      # client alias mapped to the upstream model
@@ -183,6 +187,7 @@ nonstream-keepalive-interval: 0
 #     api-key-entries:
 #       - api-key: "sk-or-v1-...b780"
 #         proxy-url: "socks5://proxy.example.com:1080" # optional: per-key proxy override
+#         # proxy-url: "direct" # optional: explicit direct connect for this credential
 #       - api-key: "sk-or-v1-...b781" # without proxy-url
 #     models: # The models supported by the provider.
 #       - name: "moonshotai/kimi-k2:free" # The actual model name.
@@ -205,6 +210,7 @@ nonstream-keepalive-interval: 0
 #     prefix: "test"                              # optional: require calls like "test/vertex-pro" to target this credential
 #     base-url: "https://example.com/api"         # e.g. https://zenmux.ai/api
 #     proxy-url: "socks5://proxy.example.com:1080" # optional per-key proxy override
+#     # proxy-url: "direct" # optional: explicit direct connect for this credential
 #     headers:
 #       X-Custom-Header: "custom-value"
 #     models:                                     # optional: map aliases to upstream model names