Order the records the way the system is learned

Jochen asked whether the order made sense. It did not -- it followed when
things happened to be decided, which after consolidation is fictional anyway
since record 5 alone folds decisions taken across a week.

Concretely wrong before: the domain statement sat at 8, after five engineering
rules; the constitution was scattered across 5, 12 and 17; the tiers landed at
15, 16, 21 and 22 with process records in between.

Now it walks: what the mesh is (1-3), its tiers from the bottom up (4-8), what
runs on them and how it gets there (9-10), how it is built (11-16), how it is
checked (17-18), how we work (19-23).

Two things made this safe rather than free. It is a permutation, not a
compaction, so the renames go through temporary names -- otherwise two files
want one slot and one is lost. And the reference rewrite is a single
simultaneous pass, because almost every number moved into a slot another number
was vacating; replacing one at a time would have cascaded and pointed things at
the wrong record while still resolving.

Verified: 284 [ADR NNNN](path) links across the repository, all with matching
text and target.

The ordering principle is now stated in 19 rather than left implicit -- the
repository already said "the numbering is the flow" about its folders, and
there was no reason for the records to be the exception.

README.md

@@ -100,7 +100,7 @@ Answered separately, a repository of its own is the better home:
   changes. Tying documents to a code branch means they merge on the code's schedule.
 - **The reviewers are different.** A design argument is not reviewed the way an
   implementation is, and it should not queue behind a build.
-- **The scope is wider than one repository.** [ADR 0008](02-DECISIONS/0008-mesh-brokers-nodes-host-agents-think.md) sends most modules out of the
+- **The scope is wider than one repository.** [ADR 0001](02-DECISIONS/0001-mesh-brokers-nodes-host-agents-think.md) sends most modules out of the
   monorepo entirely. Documentation that governs several repositories cannot live inside one
   of them.
 
@@ -110,4 +110,4 @@ than a mechanism — which is why every decision is recorded in
 [`02-DECISIONS`](02-DECISIONS/) as it is taken, and why a document that states a rule should
 say how the rule is checked.
 
-Recorded as [ADR 0011](02-DECISIONS/0011-how-this-repository-works.md).
+Recorded as [ADR 0019](02-DECISIONS/0019-how-this-repository-works.md).