update docs for http proxy (#13538)

Author: scidomino

docs/cli/configuration.md

@@ -494,6 +494,9 @@ the `excludedProjectEnvVars` setting in your `settings.json` file.
 - **`GEMINI_SANDBOX`**:
   - Alternative to the `sandbox` setting in `settings.json`.
   - Accepts `true`, `false`, `docker`, `podman`, or a custom command string.
+- **`HTTP_PROXY` / `HTTPS_PROXY`**:
+  - Specifies the proxy server to use for outgoing HTTP/HTTPS requests.
+  - Example: `export HTTPS_PROXY="http://proxy.example.com:8080"`
 - **`SEATBELT_PROFILE`** (macOS specific):
   - Switches the Seatbelt (`sandbox-exec`) profile on macOS.
   - `permissive-open`: (Default) Restricts writes to the project folder (and a
@@ -581,9 +584,6 @@ for that specific session.
   - Example: `gemini -e my-extension -e my-other-extension`
 - **`--list-extensions`** (**`-l`**):
   - Lists all available extensions and exits.
-- **`--proxy`**:
-  - Sets the proxy for the CLI.
-  - Example: `--proxy http://localhost:7890`.
 - **`--include-directories <dir1,dir2,...>`**:
   - Includes additional directories in the workspace for multi-directory
     support.

docs/get-started/configuration-v1.md

@@ -611,6 +611,9 @@ the `excludedProjectEnvVars` setting in your `settings.json` file.
 - **`GEMINI_SANDBOX`**:
   - Alternative to the `sandbox` setting in `settings.json`.
   - Accepts `true`, `false`, `docker`, `podman`, or a custom command string.
+- **`HTTP_PROXY` / `HTTPS_PROXY`**:
+  - Specifies the proxy server to use for outgoing HTTP/HTTPS requests.
+  - Example: `export HTTPS_PROXY="http://proxy.example.com:8080"`
 - **`SEATBELT_PROFILE`** (macOS specific):
   - Switches the Seatbelt (`sandbox-exec`) profile on macOS.
   - `permissive-open`: (Default) Restricts writes to the project folder (and a
@@ -699,9 +702,6 @@ for that specific session.
   - Example: `gemini -e my-extension -e my-other-extension`
 - **`--list-extensions`** (**`-l`**):
   - Lists all available extensions and exits.
-- **`--proxy`**:
-  - Sets the proxy for the CLI.
-  - Example: `--proxy http://localhost:7890`.
 - **`--include-directories <dir1,dir2,...>`**:
   - Includes additional directories in the workspace for multi-directory
     support.