Add CI publish workflow for fork packages under @argonavis-labs scope

[astrobot-houston]

Originally proposed by @steven4354 in #488. Their description is reproduced verbatim below.

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Summary

Adds a GitHub Actions workflow and a small publish script so the fork builds, tests, and publishes the four Flue packages (runtime, sdk, react, cli) to GitHub Packages under the @argonavis-labs scope on every merge to main.

• .github/workflows/publish.yml installs dependencies, builds and tests the four packages, prepares publish artifacts, and publishes to GitHub Packages.
• scripts/publish-fork.mjs rewrites package names to @argonavis-labs/flue-*, appends a fork prerelease suffix (1.0.0-beta.9-argonavis.<sha>), rewrites internal workspace:* references to npm aliases, and skips already-published versions.
• scripts/prepare-publish.mjs now includes @flue/react and avoids overwriting existing package READMEs.
• packages/react/package.json includes docs in files so React publishes docs like the other three packages.

Test plan

• Workflow YAML passes actionlint.
• node --check passes for scripts/publish-fork.mjs and scripts/prepare-publish.mjs.
• Merge to main successfully publishes all four packages to https://npm.pkg.github.com/@argonavis-labs/.
• Runner Next can install the published version via npm aliases.

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Original implementation from #488 by @steven4354