Hold a joining module at the build it ran, own its directories by its own group, and take a library only when its act is done (hq ADR 0328 review, ADR 0334)

A held module is composed exactly as before it joined, at the build its machine runs, so its port, resources and
contributions stay. A joining module's directories belong to its user and its own group, and its tools' directories
are refused closed to that group; the runner joins it where the engine can say so. A take records the root and is
taken only when the engine states the act done. Libraries' paths and verdicts count modules pulled in by a
requirement, and a unit takes the identity.

internal/inventory/migrations/0096-a-module-joins-and-a-library-has-a-group.sql

@@ -26,12 +26,14 @@ create table library_group (
 -- **A library taken** (§7). The first time a library's root on its home holds data not yet in its group, the operator
 -- is asked once for that library; on the warrant the node-engine sets the group, group write and setgid under the root,
 -- and the library is taken: kept from then on without asking. The row is the record of that act — on which machine
--- and filesystem, who approved it, under which warrant. A library whose home or filesystem changed since (it moved to
--- another machine or another disk) is not taken by that warrant, and the operator is asked again; a new take replaces
--- the row.
+-- root and filesystem, who approved it, under which warrant. A library whose home, root or filesystem changed since
+-- (it moved to another machine, path or disk) is not taken by that warrant, and the operator is asked again; a new take
+-- replaces the row.
 create table kept_library (
     library  text        primary key,
     home     text        not null,
+    -- The root it was taken at: a library whose root changed since is taken again.
+    root     text        not null check (root like '/%'),
     -- The filesystem the root was on when taken, as the engine names it without a path ("fs-<12 hex>"); empty when
     -- the engine named none.
     placed   text        not null default '',
@@ -40,5 +42,9 @@ create table kept_library (
     ask      text        not null,
     warrant  text        not null,
     -- What the node-engine answered when it started the take.
-    said     text        not null default ''
+    said     text        not null default '',
+    -- Whether the engine has stated the take's act done under this warrant: only then is the library taken. Until
+    -- then the take is under way — the library still waits, and the operator is not asked again — and an act stated
+    -- failed forgets the row, so the operator is asked again.
+    done     boolean     not null default false
 );