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/agent-required-reading-consistency.test.cjs

@@ -8,7 +8,7 @@
  * Validates that all agent .md files use the standardized <required_reading>
  * pattern and that no legacy <files_to_read> blocks remain.
  *
- * See: https://github.com/gsd-build/get-shit-done/issues/2168
+ * See: https://github.com/GSD-redux/get-shit-done-redux/issues/2168
  */
 
 const { test, describe } = require('node:test');