feat(lifecycle): plain-language generation diffs (#82)

nomarchy-what-changed wraps nvd into "N added, M removed, K updated"
summaries. nomarchy-rebuild / nomarchy-home print full nvd and toast
the one-liner; System › What changed? offers toast + floating report.
checks.what-changed fixtures nvd via NOMARCHY_NVD.

Verified: V2 — flake check --no-build; checks.what-changed green;
local smoke on real HM generations.

docs/ROADMAP.md

@@ -376,6 +376,11 @@ Design/decision records and a running log of shipped work (items marked
   `hostname == nomarchy-live` (live ISO keeps its own welcome). Toggle:
   `nomarchy.firstBootWelcome.enable`. `checks.first-boot` gates toast /
   marker / re-run silence / live skip.
+  ✓ **Generation readability (#82, `VISION § B`):** `nomarchy-what-changed`
+  wraps nvd into plain-language counts (added/removed/updated); post-switch
+  toast from `nomarchy-rebuild` / `nomarchy-home`; System › What changed?
+  (toast + floating full report). `checks.what-changed` fixtures nvd via
+  `NOMARCHY_NVD`.
 - ✓ **Hibernate double-unlock:** on resume from hibernate the LUKS
   passphrase already gates the machine, but locking hyprlock before sleep
   meant a second password. Fixed by *not locking* before an encrypted