CHANGELOG.md [Unreleased] section is out of position — violates Keep a Changelog format

[codeforester]

Problem

CHANGELOG.md places the [Unreleased] section at line 99, between [0.4.0] (line 8) and [0.3.0] (line 124):

## [0.4.0] - 2026-08-05
...
## [Unreleased]       ← wrong position
...
## [0.3.0] - 2026-08-01

The Keep a Changelog specification requires [Unreleased] to be the first version section, immediately below the introductory paragraph. Placing it in the middle of the version history means:

• Tools that parse changelogs (e.g., towncrier, GitHub release automation, changelog linters) will misread it.
• Readers skimming for unreleased changes look at the top and don't find it.

Fix

Move the ## [Unreleased] section (and its content) to immediately after the introductory paragraph, before ## [0.4.0].