Migrate posts react to pure command runner

[patosullivan]

Summary

Migrates tlon posts react to the pure command-runner architecture. Next PR will migrate everything, this is just demonstrating the shape/scale.

• Adds a pure posts react runner plus process-backed runtime deps.
• Routes only posts react ... through the new runner; all other posts paths stay on legacy dispatch.
• Preserves legacy reaction parsing, help behavior, payload formatting, and success output.
• Adds unit and source/built CLI coverage for the migrated path and a non-react legacy sentinel.

Testing

• npm run check

[Copilot]

Pull request overview

This PR migrates the tlon posts react subcommand onto the “pure command-runner” architecture, while leaving other posts subcommands on the legacy dispatcher. It adds a new pure runner with process-backed runtime deps, updates main.ts routing so only posts react uses the new runner, and adds unit + CLI matrix coverage to lock in legacy-compatible behavior and output.

Changes:

• Added a pure posts react command runner (scripts/commands/posts.ts) with legacy-compatible parsing, ID formatting, and output.
• Added a process-backed runtime dependency adapter for posts (scripts/posts-runtime.ts) and routed only posts react through it in scripts/main.ts.
• Added unit tests and CLI matrix cases covering posts react behavior and a legacy sentinel (posts unreact --help).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
scripts/posts-runtime.ts	Adds process-backed PostsDeps adapter (auth + API facade + stdout/stderr writers) for the new runner.
scripts/main.ts	Routes tlon posts react ... through the new pure runner while keeping other posts subcommands on legacy dispatch.
scripts/commands/posts.ts	Implements the pure posts react runner (arg parsing, post ID normalization, reaction call, shared error handling).
scripts/commands/posts.test.ts	Adds unit tests validating help/usage behavior, payload formatting, call ordering, and error handling semantics.
scripts/cli-test-matrix.ts	Adds CLI coverage for posts react help/auth behavior and a non-react legacy sentinel (posts unreact --help).

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[arthyn]

lgtm, just the one question

[arthyn]

not sure this should be here since this only touches react right?

[patosullivan]

Yeah, this is intentional. Since the PR changes the top-level posts dispatch, I wanted one guard proving non-react paths still stay on the legacy route. posts unreact --help is just a boundary check for that.