Bump release version to 0.9.0

[fqjony]

Why

The release workflow on latest failed while creating the Git tag:

fatal: tag 'v0.8.0' already exists\n```\n\nPR #21 merged code intended for the next release, but the package version and changelog section still pointed at `0.8.0`, which had already been published.\n\n## Changes\n\n- bump `package.json` to `0.9.0`\n- bump `package-lock.json` to `0.9.0`\n- move the unreleased changelog section from `0.8.0` to `0.9.0`\n\n## Verification\n\n- `make test`\n

[Copilot]

Pull request overview

This PR updates the project’s release metadata to avoid reusing the already-existing v0.8.0 tag and align the next release with version 0.9.0.

Changes:

• Bump package.json version from 0.8.0 to 0.9.0.
• Bump package-lock.json version fields from 0.8.0 to 0.9.0.
• Rename the top changelog section from 0.8.0 to 0.9.0.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 1 comment.

File	Description
package.json	Updates the published package version to 0.9.0.
package-lock.json	Keeps lockfile version metadata consistent with 0.9.0.
changes.md	Moves the unreleased changelog section header to 0.9.0.

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