Issue an account whose credential is not sealed, and forget an unassigned module's accounts (issue 1945, ADR 0543)

Met a second time live on 2026-10-25 at 20:04 (note 35): mesh-build-go was
assigned to ace again, and its account rows, minted at 17:19, had outlived the
unassignment. The issue minted only when no row stood, so it minted and sealed
nothing; the node had no credential and the bus no user, and the module
crash-looped 20 times. The watch still said "the grants written".

- A bus account now says when its credential was sealed to its node (migration
  0108; every account standing before is taken as sealed). An issue under the
  assign act, the assignments' watch or a registration mints only an account
  that is not issued, a row with no seal counting as none, under the store's
  lock on the account across its look, mint and seal, and marks it sealed once
  sealed. A seal that fails leaves it unsealed for the next issue.
- Unassigning a module forgets its bus accounts and their credentials on that
  node, so an assignment again issues them afresh.
- Only sealed accounts count as minted for a composition and are named in a
  grant, so the assigner, which now wants a node only once the grant names its
  account (mesh-delivery, same branch), holds the node until it is.
- The assignment's log line says which accounts were issued and sealed, or that
  they stood issued and sealed.

The process-only issue drops the atomic insert of the review of 9ff47f6a for
the lock, which also covers the seal. Tests: cases in the existing tables.
Research 072: the grants piece (memberships and credentials heard from placement).

internal/inventory/migrations/0108-a-bus-account-says-it-is-sealed.sql

@@ -0,0 +1,8 @@
+-- A bus account says when the credential minted for it was sealed to its node (novox/hq ADR 0543 §2, issue 1945). The
+-- assign act and the assignments' watch issue an account only when it is not issued: a row with no sealed credential
+-- is not issued. On 2026-10-25 at 20:04 ace's mesh-build-go had a row minted at 17:19 whose credential the node no
+-- longer held; minting nothing, the mesh sealed nothing, and the module crash-looped for its missing credential. Null
+-- while an issue mints and seals; set once the credential is handed over. Every account standing before this migration
+-- is taken as sealed: each works or worked, and its own issue sealed it.
+alter table bus_user add column sealed_at timestamptz;
+update bus_user set sealed_at = minted_at;