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.

AGENTS.md

@@ -1,7 +1,7 @@
 # Agent instructions — Novox HQ
 
 This repository is the source of truth for Novox's mission, research, design and decisions —
-today almost entirely those of **Novox Mesh**, its first product ([ADR 0011](02-DECISIONS/0011-how-this-repository-works.md)). Implementation lives in the code repositories (see
+today almost entirely those of **Novox Mesh**, its first product ([ADR 0019](02-DECISIONS/0019-how-this-repository-works.md)). Implementation lives in the code repositories (see
 [`00-META/repos.md`](00-META/repos.md)).
 
 Before changing anything here, read the playbooks in