Release flux-opencode

Bumps version across all manifest files, commits, and creates a GitHub release.

Arguments

$ARGUMENTS format: <version> [--title "Release title"]

Examples:

• /flux:release v0.3.0
• /flux:release v0.3.0 --title "Security Suite"

Version Files (ALL must be updated)

1. package.json → "version": "X.Y.Z"
2. .opencode/version → X.Y.Z
3. README.md → version badge
4. CHANGELOG.md → move [Unreleased] entries under new heading