release: tag a first release and add release automation

Problem

nuklear_console has never tagged a release (gh release list is empty), while CMakeLists.txt declares VERSION 0.1.1. Downstream users — including CMake FetchContent consumers, who currently must pin GIT_TAG master (as this repo itself does for nuklear_gamepad) — have nothing stable to pin, and there's no changelog marking what shipped.

The project has matured a lot recently (list_view search/dynamic-height/Home-End, SDL3 native file dialogs, keyboard+mouse input flags, ASAN CI), so a first tagged release would capture a good snapshot.

Suggested Implementation

• Decide the version (suggest v0.2.0 given the API additions since 0.1.1 was written) and bump CMakeLists.txt to match.
• Tag and create a GitHub release with brief notes summarizing highlights since the project started (widgets, input support, SDL3 dialogs, test suite).
• Add lightweight automation: a workflow triggered on v* tag push that creates the GitHub release with generated notes (gh release create --generate-notes or softprops/action-gh-release). Since this is a header-only library, no build artifacts are needed — the source tarball suffices.
• Document the release process in the README Development section (bump CMake version → tag → workflow does the rest).

QA

• v0.2.0 appears under Releases with generated notes.
• FetchContent with GIT_TAG v0.2.0 builds the test suite successfully.
• CMake version and git tag agree.

Context

• Priority 7 (final item) of the 2026-07-11 planning session — do this after the bug fixes land (#276, #277) so the first tagged release includes them.
• Blocked by (soft): #276, #277.

Start by reviewing CMakeLists.txt, the README Development section, and the existing GitHub Actions workflows, while checking the status of blockers #276 and #277. Implement the documented version, tag, and release workflow process; done means the v0.2.0 release appears with generated notes, CMake and the tag agree, and FetchContent using v0.2.0 builds the test suite.