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/changeset-github-release-notes.test.cjs

@@ -109,7 +109,7 @@ describe('changeset github release notes: tag-range renderer (#3382)', () => {
       fromRef: 'v1.0.0',
       toRef: 'v1.0.1',
       repoSlug: 'example/project',
-      installCommand: 'npx get-shit-done-cc@latest',
+      installCommand: 'npx get-shit-done-redux@latest',
     });
     assert.equal(fs.readFileSync(output, 'utf8'), generated.body);
   });