ci: rename build-nsInnoUnp.yml -> build-ns7zip.yml; update doc refs

Workflow now targets Simone/nsis-plugin-ns7zip. Renamed the file and
the workflow `name:`, and updated all references in active docs
(plans/archived and docs/archived left as frozen history).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

plans/idea-1-python-rewrite.md

@@ -202,7 +202,7 @@ gitea/                     # workflow + actions invariati
 - [ ] `pytest` verde con coverage minima 70% su `src/ci_orchestrator/`
 - [ ] `ruff check` + `mypy --strict` puliti su tutto `src/`
 - [ ] `lint.yml` aggiornato: PSSA per file PS legacy + ruff/mypy per Python
-- [ ] Workflow `build-nsInnoUnp.yml` PASS su matrice Windows + Linux
+- [ ] Workflow `build-ns7zip.yml` PASS su matrice Windows + Linux
 - [ ] Smoke test (`Test-Smoke.ps1` o equivalente Python) PASS
 - [ ] Capacity burn-in 4 job concorrenti PASS
 - [ ] `README.md`, `AGENTS.md`, `docs/ARCHITECTURE.md`, `docs/HOST-SETUP.md` aggiornati