fix(network): use usize::try_from instead of truncating cast

Replace `u64 as usize` casts with `usize::try_from().unwrap_or(usize::MAX)`
in network client (content_length) and Python bindings (limits).
Prevents silent truncation on 32-bit platforms.

Closes #430

Author: claude

crates/bashkit-python/src/lib.rs

@@ -219,10 +219,10 @@ impl PyBash {
 
         let mut limits = ExecutionLimits::new();
         if let Some(mc) = max_commands {
-            limits = limits.max_commands(mc as usize);
+            limits = limits.max_commands(usize::try_from(mc).unwrap_or(usize::MAX));
         }
         if let Some(mli) = max_loop_iterations {
-            limits = limits.max_loop_iterations(mli as usize);
+            limits = limits.max_loop_iterations(usize::try_from(mli).unwrap_or(usize::MAX));
         }
         builder = builder.limits(limits);
 
@@ -313,10 +313,10 @@ impl PyBash {
                 }
                 let mut limits = ExecutionLimits::new();
                 if let Some(mc) = max_commands {
-                    limits = limits.max_commands(mc as usize);
+                    limits = limits.max_commands(usize::try_from(mc).unwrap_or(usize::MAX));
                 }
                 if let Some(mli) = max_loop_iterations {
-                    limits = limits.max_loop_iterations(mli as usize);
+                    limits = limits.max_loop_iterations(usize::try_from(mli).unwrap_or(usize::MAX));
                 }
                 builder = builder.limits(limits);
                 *bash = builder.build();
@@ -396,10 +396,10 @@ impl BashTool {
 
         let mut limits = ExecutionLimits::new();
         if let Some(mc) = max_commands {
-            limits = limits.max_commands(mc as usize);
+            limits = limits.max_commands(usize::try_from(mc).unwrap_or(usize::MAX));
         }
         if let Some(mli) = max_loop_iterations {
-            limits = limits.max_loop_iterations(mli as usize);
+            limits = limits.max_loop_iterations(usize::try_from(mli).unwrap_or(usize::MAX));
         }
         builder = builder.limits(limits);
 
@@ -622,10 +622,10 @@ impl ScriptedTool {
         if self.max_commands.is_some() || self.max_loop_iterations.is_some() {
             let mut limits = ExecutionLimits::new();
             if let Some(mc) = self.max_commands {
-                limits = limits.max_commands(mc as usize);
+                limits = limits.max_commands(usize::try_from(mc).unwrap_or(usize::MAX));
             }
             if let Some(mli) = self.max_loop_iterations {
-                limits = limits.max_loop_iterations(mli as usize);
+                limits = limits.max_loop_iterations(usize::try_from(mli).unwrap_or(usize::MAX));
             }
             builder = builder.limits(limits);
         }

crates/bashkit/src/network/client.rs

@@ -233,7 +233,7 @@ impl HttpClient {
 
         // Check Content-Length header to fail fast on large responses
         if let Some(content_length) = response.content_length() {
-            if content_length as usize > self.max_response_bytes {
+            if usize::try_from(content_length).unwrap_or(usize::MAX) > self.max_response_bytes {
                 return Err(Error::Network(format!(
                     "response too large: {} bytes (max: {} bytes)",
                     content_length, self.max_response_bytes
@@ -416,7 +416,7 @@ impl HttpClient {
 
         // Check Content-Length header to fail fast on large responses
         if let Some(content_length) = response.content_length() {
-            if content_length as usize > self.max_response_bytes {
+            if usize::try_from(content_length).unwrap_or(usize::MAX) > self.max_response_bytes {
                 return Err(Error::Network(format!(
                     "response too large: {} bytes (max: {} bytes)",
                     content_length, self.max_response_bytes
@@ -528,6 +528,15 @@ mod tests {
         assert!(result.unwrap_err().to_string().contains("access denied"));
     }
 
+    #[test]
+    fn test_u64_to_usize_no_truncation() {
+        // On 64-bit: fits fine. On 32-bit: saturates to usize::MAX rather than truncating.
+        let large: u64 = 5_368_709_120; // 5GB
+        let result = usize::try_from(large).unwrap_or(usize::MAX);
+        // Should never silently become a smaller value
+        assert!(result >= large.min(usize::MAX as u64) as usize);
+    }
+
     // Note: Integration tests that actually make network requests
     // should be in a separate test file and marked with #[ignore]
     // to avoid network dependencies in unit tests.