feat: API timeout config, Retry-After header support, and configurable retry

- Add TimeoutConfig to HTTP client builder with connect_timeout (30s)
  and request_timeout (5min) defaults, configurable via
  CLAW_API_CONNECT_TIMEOUT and CLAW_API_REQUEST_TIMEOUT env vars
- Add with_timeout() builder to both AnthropicClient and
  OpenAiCompatClient for per-client timeout configuration
- Parse Retry-After header on 429 responses and use it to override
  exponential backoff delay when present
- Add ApiTimeoutConfig to runtime config with apiTimeout settings
  in ~/.claw/settings.json (connectTimeout, requestTimeout, maxRetries)
- Add retry_after field to ApiError::Api for propagating rate limit
  backoff hints through the retry pipeline

rust/crates/rusty-claude-cli/src/main.rs

@@ -10547,7 +10547,8 @@ mod tests {
             body: String::new(),
             retryable: true,
             suggested_action: None,
-        };
+            retry_after: None,
+};
 
         let rendered = format_user_visible_api_error("session-issue-22", &error);
         assert!(rendered.contains("provider_internal"));
@@ -10570,7 +10571,8 @@ mod tests {
                 body: String::new(),
                 retryable: true,
                 suggested_action: None,
-            }),
+                retry_after: None,
+}),
         };
 
         let rendered = format_user_visible_api_error("session-issue-22", &error);
@@ -10634,7 +10636,8 @@ mod tests {
             body: String::new(),
             retryable: false,
             suggested_action: None,
-        };
+            retry_after: None,
+};
 
         let rendered = format_user_visible_api_error("session-issue-32", &error);
         assert!(rendered.contains("context_window_blocked"), "{rendered}");
@@ -10701,7 +10704,8 @@ mod tests {
                 body: String::new(),
                 retryable: false,
                 suggested_action: None,
-            }),
+                retry_after: None,
+}),
         };
 
         let rendered = format_user_visible_api_error("session-issue-32", &error);