Number with a dot before `e` in scientific notation returns two dots in JavaScript

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Choose one: is this a bug report or feature request? Bug report

### Input Code

Example code:
```coffee
1.e1
```
And another example:
```coffee
1.e-1
```

### Expected Behavior

```js
1.e1;
```
and
```js
1.e-1;
```
### Current Behavior

```js
1..e1;
```
and
```js
1..e - 1;
```
### Possible Solution

Remove a dot or add a `0` after the dot if there is no number after the dot and before the `e` in scientific notation.
### Context

Using scientific notation with decimals
### Environment

* CoffeeScript version: 2.7.0

Start by compiling the reported CoffeeScript inputs `1.e1` and `1.e-1` and compare the generated JavaScript with the expected output. Trace the compiler's handling of numeric literals around the exponent marker, then add regression coverage showing that both forms produce one dot and preserve the exponent expression.

Written by the indexing model from the issue text.