docs(adr): shared spaces, decided further, in six steps

ADR 0044 records the answers to its open questions: a shared studyset
passes on when its owner leaves or deletes their account (D11); an
agent's token lapses after 90 days unused (D12); an invitation by handle
waits for someone who never used the app (D13); and sharing copies the
studyset under new IDs into the shared space (D14), since the sync
engine's delete is soft and a row's ID can't be inserted into another
space. Its Steps section orders the work, starting with the community's
confirmation (D8, D9).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

docs/adr/0044-shared-spaces-and-collaboration.md

@@ -2,8 +2,9 @@
 
 - **Status:** decided 10 Nov 2026 by the developer: D8 is their own request, D9 and D10
   their choices over the agent's recommendations (all ticked at first; agents editing
-  directly), D1 to D7 the agent's recommendations, which they chose. Not built yet; the
+  directly), D1 to D7 the agent's recommendations, which they chose; D11 to D13 the
-  open questions below come first.
+  agent's recommendations, which they chose on 11 Nov 2026, D14 too. Not built yet;
+  the steps below.
 - **Builds on:** ADR 0005 (publishing, reports and suggestions), ADR 0014 (the module),
   ADR 0016 (one account across an instance), ADR 0017 (key pairs), ADR 0019 (private
   studysets), ADR 0021 (operators and assistants).
@@ -63,20 +64,44 @@ member reads everything in the space.
   decisions, accepted suggestions applied by their item) are the start: they become
   suggestions within a shared space too, not only on published releases.
 
+- **D11.** **A shared studyset passes on.** Leaving, the Owner picks the next Owner
+  first. Deleting their account, ownership passes by itself to the Editor who joined
+  first, else to the Viewer who joined first; only with no other member does the
+  studyset go with them.
+- **D12.** **An agent's token lapses after 90 days unused;** while used it has no fixed
+  end, the owner revokes it any time, and their Profile shows when it was last used.
+- **D13.** **An invitation by @handle waits** for someone who has an account on the
+  instance's register but has never used the app: they find it in their Inbox the first
+  time they sign in to it, and the inviter sees them as invited until then.
+
+- **D14.** **Sharing copies the studyset under new IDs** into the shared space, rewrites
+  what names its rows (reviews, tags, the learning path, files) and deletes the old ones,
+  as ADR 0019's rewrites do; the fork stays as it is. Found 11 Nov 2026: the engine's
+  delete is soft (`insteadOfDelete`: the domain row stays, hidden by a tombstone in its
+  space's `crdt_data_rows`), and a synced table's primary key is the row's ID alone, so
+  the same ID can't be inserted into another space; teaching the engine to move a row
+  was the other way, set aside as a deeper change to its merge, kept on every rebase.
+
+## Steps
+
+1. **Share with the community's confirmation** (D8, D9), needing nothing else here.
+2. **Shared spaces in halkyon_base** (D1, D2, D11, D13): the module's tables (a shared
+   space, its members and roles, its Owner), its endpoints with their denial tests,
+   the engine's grants kept in step, the hand-on as an account is deleted.
+3. **Keys** (D3): a private studyset's key wrapped to each member's key pair.
+4. **Learn shares a studyset** (D14): the copy, *Manage collaborators* (invite by
+   @handle, the members, their roles, leaving), each member's own reviews.
+5. **Invitations by email and by link** (D4, D5), the Inbox.
+6. **Agents** (D6, D7, D10, D12).
+
 ## Open questions, before building
 
-- **Moving rows between spaces.** A studyset's rows are in its owner's personal space;
+- **Moving rows between spaces.** Decided: D14.
-  sharing moves them into a new shared space. Row IDs are unique across a table and the
-  engine keeps a deleted row's tombstone until its space goes, so a row can't simply be
-  deleted in one space and inserted in another under the same ID. Either the engine
-  learns to move a row between spaces (a change to our fork), or sharing copies the tree
-  under new IDs and rewrites what names them (cards' reviews, tags, the learning path),
-  as ADR 0019's rewrites do with keys. To try against the fork first.
 - **Whose reviews.** A Viewer's or Editor's schedule for a shared card stays in their own
   space, keyed by the card's ID; the card's own review rows today assume one learner.
-- **Handing on and leaving.** An Owner leaving must hand the studyset on first, or it
+- **Handing on and leaving.** Decided: D11. To build: the account's deletion hands the
-  goes with them, as their account's deletion deletes their spaces.
+  shared spaces it owns on before it deletes the person's own.
-- **Members across services.** On an instance with a register (ADR 0016), handles are
+- **Members across services.** Decided: D13. A member of a Learn studyset needs no Todo
-  the register's; a member of a Learn studyset needs no Todo account and the reverse.
+  account, and the reverse.
 - **The agent's token:** made and revoked in the owner's Profile, scoped to the agent's
-  account, never shown again after making; whether it expires.
+  account, never shown again after making; its lapse decided: D12.