ADR 0009: one Werkator instance serves a set of repositories

Records the tenet revision and its shape: instance registry and
instance keys in ~/.werkator.yml (one instance per OS user), optional
repo defaults in an explicit defaults: block merged below every repo's
own layers, repo config unchanged in each repository, registry-wins
precedence, basename repo names. Rejected: a federation dashboard over
single-repo instances (keeps N services), and the status quo.
Konzept/AGENTS architecture wording changes only when the
implementation lands; the decision list carries 0009 now.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

AGENTS.md

@@ -81,6 +81,7 @@ All major decisions are in `docs/adrs/`. Run `adr-status` (after `source .envrc`
 - **Runtime bundle distribution**: `./gradlew runtimeBundle` builds a jlink-trimmed JRE + jar tarball for hosts without a Java runtime; GraalVM native image and a containerized runtime were rejected (ADR 0006)
 - **Build definitions**: a top-level `builds` section of named builds with `trigger` blocks replaces the branch-owned `autoBuild` schedules (ADR 0007)
 - **bwrap build runtime**: on hosts without root and without Docker (Hostsharing Managed Webspaces), builds run in a `bwrap` user-namespace sandbox over a prepared rootfs — filesystem isolation only, network and uid shared with the host; proot/fakechroot and unisolated native builds were rejected (ADR 0008)
+- **Multi-repo instance**: one instance serves a registry of self-contained repositories (instance config in `~/.werkator.yml`, repo config in each repo); revises the one-instance-per-repository tenet, implementation planned as `docs/plan/22-multi-repo.md` (ADR 0009)
 
 ## Skills