implement $ENV:[env-var]:[fallback] config replacements

docs/docs/config.mdx

@@ -95,34 +95,34 @@ wsh editconfig
 | window:dimensions                    | string   | set the default dimensions for new windows using the format "WIDTHxHEIGHT" (e.g. "1920x1080"). when a new window is created, these dimensions will be automatically applied. The width and height values should be specified in pixels.                       |
 | telemetry:enabled                    | bool     | set to enable/disable telemetry                                                                                                                                                                                                                               |
 
-For reference, this is the current default configuration (v0.10.4):
+For reference, this is the current default configuration (v0.11.5):
 
 ```json
 {
-  "ai:preset": "ai@global",
-  "ai:model": "gpt-4o-mini",
-  "ai:maxtokens": 2048,
-  "ai:timeoutms": 60000,
-  "app:defaultnewblock": "term",
-  "autoupdate:enabled": true,
-  "autoupdate:installonquit": true,
-  "autoupdate:intervalms": 3600000,
-  "conn:askbeforewshinstall": true,
-  "conn:wshenabled": true,
-  "editor:minimapenabled": true,
-  "web:defaulturl": "https://github.com/wavetermdev/waveterm",
-  "web:defaultsearch": "https://www.google.com/search?q={query}",
-  "window:tilegapsize": 3,
-  "window:maxtabcachesize": 10,
-  "window:nativetitlebar": true,
-  "window:magnifiedblockopacity": 0.6,
-  "window:magnifiedblocksize": 0.9,
-  "window:magnifiedblockblurprimarypx": 10,
-  "window:magnifiedblockblursecondarypx": 2,
-  "window:confirmclose": true,
-  "window:savelastwindow": true,
-  "telemetry:enabled": true,
-  "term:copyonselect": true
+    "ai:preset": "ai@global",
+    "ai:model": "gpt-4o-mini",
+    "ai:maxtokens": 2048,
+    "ai:timeoutms": 60000,
+    "app:defaultnewblock": "term",
+    "autoupdate:enabled": true,
+    "autoupdate:installonquit": true,
+    "autoupdate:intervalms": 3600000,
+    "conn:askbeforewshinstall": true,
+    "conn:wshenabled": true,
+    "editor:minimapenabled": true,
+    "web:defaulturl": "https://github.com/wavetermdev/waveterm",
+    "web:defaultsearch": "https://www.google.com/search?q={query}",
+    "window:tilegapsize": 3,
+    "window:maxtabcachesize": 10,
+    "window:nativetitlebar": true,
+    "window:magnifiedblockopacity": 0.6,
+    "window:magnifiedblocksize": 0.9,
+    "window:magnifiedblockblurprimarypx": 10,
+    "window:magnifiedblockblursecondarypx": 2,
+    "window:confirmclose": true,
+    "window:savelastwindow": true,
+    "telemetry:enabled": true,
+    "term:copyonselect": true
 }
 ```
 
@@ -134,6 +134,17 @@ files as well: `termthemes.json`, `presets.json`, and `widgets.json`.
 
 :::
 
+## Environment Variable Resolution
+
+To avoid putting secrets directly in config files, Wave supports environment variable resolution using `$ENV:VARIABLE_NAME` or `$ENV:VARIABLE_NAME:fallback` syntax.  This works for any string value in any config file (settings.json, presets.json, ai.json, etc.).
+
+```json
+{
+  "ai:apitoken": "$ENV:OPENAI_APIKEY",
+  "ai:baseurl": "$ENV:AI_BASEURL:https://api.openai.com/v1"
+}
+```
+
 ## WebBookmarks Configuration
 
 WebBookmarks allows you to store and manage web links with customizable display preferences. The bookmarks are stored in a JSON file (`bookmarks.json`) as a key-value map where the key (`id`) is an arbitrary identifier for the bookmark. By convention, you should start your ids with "bookmark@". In the web widget, you can pull up your bookmarks using <Kbd k="Cmd:o"/>

pkg/wconfig/settingsconfig.go

@@ -327,6 +327,65 @@ func isTrailingCommaError(barr []byte, offset int) bool {
 	return false
 }
 
+func resolveEnvReplacements(m waveobj.MetaMapType) {
+	if m == nil {
+		return
+	}
+
+	for key, value := range m {
+		switch v := value.(type) {
+		case string:
+			if resolved, ok := resolveEnvValue(v); ok {
+				m[key] = resolved
+			}
+		case map[string]interface{}:
+			resolveEnvReplacements(waveobj.MetaMapType(v))
+		case []interface{}:
+			resolveEnvArray(v)
+		}
+	}
+}
+
+func resolveEnvArray(arr []interface{}) {
+	for i, value := range arr {
+		switch v := value.(type) {
+		case string:
+			if resolved, ok := resolveEnvValue(v); ok {
+				arr[i] = resolved
+			}
+		case map[string]interface{}:
+			resolveEnvReplacements(waveobj.MetaMapType(v))
+		case []interface{}:
+			resolveEnvArray(v)
+		}
+	}
+}
+
+func resolveEnvValue(value string) (string, bool) {
+	if !strings.HasPrefix(value, "$ENV:") {
+		return "", false
+	}
+
+	envSpec := value[5:] // Remove "$ENV:" prefix
+	parts := strings.SplitN(envSpec, ":", 2)
+	envVar := parts[0]
+	var fallback string
+	if len(parts) > 1 {
+		fallback = parts[1]
+	}
+
+	// Get the environment variable value
+	if envValue, exists := os.LookupEnv(envVar); exists {
+		return envValue, true
+	}
+
+	// Return fallback if provided, otherwise return empty string
+	if fallback != "" {
+		return fallback, true
+	}
+	return "", true
+}
+
 func readConfigHelper(fileName string, barr []byte, readErr error) (waveobj.MetaMapType, []ConfigError) {
 	var cerrs []ConfigError
 	if readErr != nil && !os.IsNotExist(readErr) {
@@ -353,6 +412,12 @@ func readConfigHelper(fileName string, barr []byte, readErr error) (waveobj.Meta
 		}
 		cerrs = append(cerrs, ConfigError{File: fileName, Err: err.Error()})
 	}
+
+	// Resolve environment variable replacements
+	if rtn != nil {
+		resolveEnvReplacements(rtn)
+	}
+
 	return rtn, cerrs
 }