v0.270.0: no update for a current app (R-679); an interrupted install is reported (R-681); a restore brings back the pinned version's health check (R-669); R-674

Five red-proofs. MinAgent 0.131.0 unchanged.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/scripts/i18n_go_keys.json

@@ -32,6 +32,7 @@
     "update.phase.copying": "BORN AS A KEY, v0.263.0 (R-637, the undo) -- a NEW sentence, never a Go literal. Pinned by internal/stacks/undo_test.go and internal/web/undo_page_test.go.",
     "update.phase.undoing": "BORN AS A KEY, v0.263.0 (R-637, the undo) -- a NEW sentence, never a Go literal. Pinned by internal/stacks/undo_test.go and internal/web/undo_page_test.go.",
     "update.phase.undone": "BORN AS A KEY, v0.263.0 (R-637, the undo) -- a NEW sentence, never a Go literal. Pinned by internal/stacks/undo_test.go and internal/web/undo_page_test.go.",
+    "err.stacks.update_already_current": "BORN AS A KEY, v0.270.0 (R-679) -- the already-at-the-head refusal. Pinned by TestR679_CurrentAppIsRefused.",
     "err.stacks.update_downgrade": "BORN AS A KEY, v0.260.0 (R-524) -- the downgrade refusal. A NEW sentence, never a Go literal. Pinned by TestR524_PreflightRefusesDowngrade, which asserts the refusal carries a Cause so api.Router.errText can render it.",
     "err.stacks.update_self_updating": "BORN AS A KEY, v0.261.0 (R-608) -- the app update refuses to start while the controller is swapping itself. A NEW sentence, never a Go literal. Pinned by TestR608_PreflightRefusesWhileTheControllerSwaps, which asserts the refusal carries a Cause so errText can render it.",
     "func.state.degraded": "slice 0 -- pinned by TestLocaleFuncsHungarianBundleMatchesFuncMap",