feat(security): harden gateway boundaries and usage policies

Consolidate subscription usage policy enforcement, privacy-safe persistence, and gateway security hardening into one reviewable change.

Includes bounded HTTP and execution envelopes, header and protocol guards, DNS and relay validation, authentication and secret projection hardening, secure backup/install paths, and regression coverage.

crates/aether-provider/transport/src/windsurf/cascade.rs

@@ -23,7 +23,7 @@ OUTPUT RULES:
 
 Violating these rules will produce broken output for the end user. Stay in chat-API mode at all times."#;
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Clone, PartialEq, Eq)]
 pub struct CascadeStep {
     pub step_type: u64,
     pub status: u64,
@@ -36,12 +36,44 @@ pub struct CascadeStep {
     pub usage: Option<CascadeUsage>,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+impl fmt::Debug for CascadeStep {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter
+            .debug_struct("CascadeStep")
+            .field("step_type", &self.step_type)
+            .field("status", &self.status)
+            .field("text_len", &self.text.len())
+            .field("response_text_len", &self.response_text.len())
+            .field("modified_text_len", &self.modified_text.len())
+            .field("thinking_len", &self.thinking.len())
+            .field("error_text_len", &self.error_text.len())
+            .field("has_native_tool", &self.native_tool.is_some())
+            .field("usage", &self.usage)
+            .finish()
+    }
+}
+
+#[derive(Clone, PartialEq, Eq)]
 pub struct CascadeNativeToolStep {
     pub kind: String,
     pub arguments: Value,
 }
 
+impl fmt::Debug for CascadeNativeToolStep {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter
+            .debug_struct("CascadeNativeToolStep")
+            .field("kind", &self.kind)
+            .field(
+                "arguments_bytes",
+                &serde_json::to_vec(&self.arguments)
+                    .ok()
+                    .map(|bytes| bytes.len()),
+            )
+            .finish()
+    }
+}
+
 #[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
 pub struct CascadeUsage {
     pub input_tokens: u64,
@@ -60,13 +92,23 @@ impl CascadeUsage {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Clone, PartialEq, Eq)]
 pub struct CascadeImage {
     pub base64_data: String,
     pub mime_type: String,
 }
 
-#[derive(Debug, Clone, Default, PartialEq, Eq)]
+impl fmt::Debug for CascadeImage {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter
+            .debug_struct("CascadeImage")
+            .field("base64_data_len", &self.base64_data.len())
+            .field("mime_type", &self.mime_type)
+            .finish()
+    }
+}
+
+#[derive(Clone, Default, PartialEq, Eq)]
 pub struct SendCascadeMessageOptions {
     pub tool_preamble: Option<String>,
     pub images: Vec<CascadeImage>,
@@ -75,6 +117,34 @@ pub struct SendCascadeMessageOptions {
     pub native_allowlist: Vec<String>,
 }
 
+impl fmt::Debug for SendCascadeMessageOptions {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter
+            .debug_struct("SendCascadeMessageOptions")
+            .field(
+                "tool_preamble_len",
+                &self.tool_preamble.as_ref().map(String::len),
+            )
+            .field("image_count", &self.images.len())
+            .field(
+                "image_bytes",
+                &self
+                    .images
+                    .iter()
+                    .map(|image| image.base64_data.len())
+                    .sum::<usize>(),
+            )
+            .field("additional_steps_count", &self.additional_steps.len())
+            .field(
+                "additional_steps_bytes",
+                &self.additional_steps.iter().map(Vec::len).sum::<usize>(),
+            )
+            .field("native_mode", &self.native_mode)
+            .field("native_allowlist_count", &self.native_allowlist.len())
+            .finish()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct CascadeBuildError {
     message: String,

crates/aether-provider/transport/src/windsurf/proto.rs

@@ -8,19 +8,42 @@ pub enum WireType {
     Fixed32 = 5,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Clone, PartialEq, Eq)]
 pub enum FieldValue {
     Varint(u64),
     Bytes(Vec<u8>),
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+impl fmt::Debug for FieldValue {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Varint(value) => formatter.debug_tuple("Varint").field(value).finish(),
+            Self::Bytes(bytes) => formatter
+                .debug_struct("Bytes")
+                .field("len", &bytes.len())
+                .finish(),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq)]
 pub struct Field {
     pub number: u32,
     pub wire_type: WireType,
     pub value: FieldValue,
 }
 
+impl fmt::Debug for Field {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter
+            .debug_struct("Field")
+            .field("number", &self.number)
+            .field("wire_type", &self.wire_type)
+            .field("value", &self.value)
+            .finish()
+    }
+}
+
 impl Field {
     pub fn bytes(&self) -> &[u8] {
         match &self.value {
@@ -138,7 +161,7 @@ pub fn parse_fields(buf: &[u8]) -> Result<Vec<Field>, ProtoError> {
             other => {
                 return Err(ProtoError::new(format!(
                     "unknown wire type {other} at offset {pos}"
-                )))
+                )));
             }
         };
         let value = match wire_type {