chore: rebrand to GSD-redux/get-shit-done-redux

Mirror of code, issues, and PRs from the upstream gsd-build/get-shit-done,
which appears compromised or abandoned (maintainer unreachable since
2026-04-01; $GSD token linked to rug-pull).

- Adds rebrand notice block at top of English README
- Removes $GSD token badge and @gsd_foundation X badge (keeps Discord)
- Renames npm packages: get-shit-done-cc -> get-shit-done-redux,
  @gsd-build/sdk -> @gsd-redux/sdk
- Updates all repo URLs across docs, workflows, package.json, bin/
- Updates ci@gsd-build -> ci@gsd-redux in workflow git identities
- Leaves CHANGELOG and .changeset/* alone (historical, time-stamped)

tests/bug-3562-codex-install-skill-surface.test.cjs

@@ -11,7 +11,7 @@ process.env.GSD_TEST_MODE = '1';
  * commands from skills/<name>/SKILL.md. Prior installer logic ("Codex now
  * discovers official skills from .agents/skills") was based on an assumption
  * that does not match the shipping Codex CLI behavior, leaving users with
- * workflows on disk and no $gsd-* entrypoints after `npx get-shit-done-cc
+ * workflows on disk and no $gsd-* entrypoints after `npx get-shit-done-redux
  * --codex --global`.
  *
  * Fix: re-wire copyCommandsAsCodexSkills() back into the install dispatch path