chore: release v0.15.4 (#2269)

<!-- CURSOR_SUMMARY -->
> [!NOTE]
> **Release 0.15.4**
> 
> - Update `CHANGELOG.md` with 0.15.4 notes: add support for `.tofu`
wherever `.tf` is considered (stack detection via `create
--all-terraform`, `--changed` change detection, and `tm_vendor`
downloads)
> - Bump `VERSION` from `0.15.4-dev` to `0.15.4`
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
8303041. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: snakster

CHANGELOG.md

@@ -20,7 +20,7 @@ Given a version number `MAJOR.MINOR.PATCH`, we increment the:
 - Backward compatibility in versions `0.0.z` is **not guaranteed** when `z` is increased.
 - Backward compatibility in versions `0.y.z` is **not guaranteed** when `y` is increased.
 
-## Unreleased
+## 0.15.4
 
 ### Added
 

VERSION

@@ -1 +1 @@
-0.15.4-dev
+0.15.4