docs(canon): define prj- project repository flavor

Publish project-repository-flavor_v0.1 with naming, GOAL.md (not durable
INTENT.md), authority boundary, lifecycle, residuals, and archive rules.
Close ADR-005 deferred naming and CUST-WP-0050 D1a; cross-link from the
repo classification standard.

canon/architecture/adr-005-cross-repo-workplans-project-repos.md

@@ -74,10 +74,17 @@ draft → active → completed → archived
 
 ## Naming
 
-Project repos SHOULD be identifiable as such (e.g. a `proj-<slug>` prefix or a
-dedicated grouping). Exact convention is deferred to `CUST-WP-0050` rollout
-(tracked as an open question there), but the lifecycle and ownership rules above
-are fixed by this ADR.
+Project repos MUST use the `prj-<kebab-slug>` prefix.
+
+Exact naming, required files (`GOAL.md` instead of durable-product
+`INTENT.md`), authority boundary, residual handoff, and archive procedure are
+defined in:
+
+`canon/standards/project-repository-flavor_v0.1.md`
+
+That standard closes the naming open question previously deferred to
+`CUST-WP-0050` (D1a). The illustrative `proj-` form mentioned in earlier drafts
+is not used for new repositories.
 
 ## Consequences