chore(#518): rename npm package + bin to @opengsd/gsd-core (#519)

* chore: rename npm package + bin to @opengsd/gsd-core (functional)

- package.json: name @opengsd/get-shit-done-redux → @opengsd/gsd-core,
  bin key get-shit-done-redux → gsd-core, repository/homepage/bugs URLs
- package-lock.json: regenerated (npm install --package-lock-only)
- tests/**, scripts/**, bin/**, .github/**, agents/**, commands/**,
  get-shit-done/bin/**, get-shit-done/workflows/**:
  applied the 4-rule replacement (scoped npm ref, GitHub repo path,
  bin/clone invocations) per #505 single-source refactor

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* docs: sweep live references to @opengsd/gsd-core

Update all live documentation (README.md + translations, docs/**,
CONTRIBUTING.md, VERSIONING.md, SECURITY.md, CONTEXT.md,
docs/CANARY.md) to reflect the renamed package and repository.

Rules applied:
- @opengsd/get-shit-done-redux → @opengsd/gsd-core (scoped npm name)
- open-gsd/get-shit-done-redux → open-gsd/gsd-core (GitHub repo)
- GSD-redux/get-shit-done-redux → open-gsd/gsd-core (stale badge org)
- bare bin/clone refs → gsd-core

CHANGELOG.md, docs/adr/**, docs/RELEASE-*.md, docs/research/**,
and .changeset/** are preserved byte-identical.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix: add negative lookbehind to slash-command regex in bug-2954 test

The extractSlashReferences regex matched /gsd-core inside npm package
URLs (@opengsd/gsd-core), producing a false /gsd:core command reference.
Adding a negative lookbehind (?<![a-z]) excludes matches preceded by a
letter, so only standalone /gsd-<cmd> and /gsd:<cmd> tokens are found.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore(#518): add changeset for package rename

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* test(#518): update package-identity expectations to the renamed coordinates

The rebase regenerated the seam to @opengsd/gsd-core (bin gsd-core, repo
open-gsd/gsd-core). The #498 seam tests assert deriveIdentity against the REAL
package.json, so their expected literals must follow the rename. The drift-lint
unit test is left as-is — its SEAM is a self-consistent fixture and its
stale-literal detection cases would shift if altered; the live-repo scan in it
already passes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

docs/contributing/bootstrap.md

@@ -36,8 +36,8 @@ will read it.
 
 ```bash
 # 1. Clone
-git clone https://github.com/open-gsd/get-shit-done-redux.git
-cd get-shit-done-redux
+git clone https://github.com/open-gsd/gsd-core.git
+cd gsd-core
 
 # 2. Activate the pinned Node version
 nvm use          # nvm
@@ -67,7 +67,7 @@ See https://docs.npmjs.com/cli/v10/commands/npm-ci
 | `npm run test:integration` | Integration tests |
 | `npm run build:sdk` | Rebuild the SDK dist (required before first test run) |
 
-> `npm run check:integrity` — available once [#114](https://github.com/open-gsd/get-shit-done-redux/issues/114) merges.
+> `npm run check:integrity` — available once [#114](https://github.com/open-gsd/gsd-core/issues/114) merges.
 
 ---