Release 2.0.0 — explicit monorepo_url, drop first-target-host inference

Breaking change. The monorepo's gitea host was previously inferred from the
first target's subrepo_url, silently coupling the two and breaking on any
multi-host setup (monorepo on host A, target on host B). v2.0.0 replaces the
inference with a required josh.monorepo_url field that mirrors subrepo_url —
same parsing, same SSH/HTTPS auth options, same shape.

- schema_version: 2 is now required; v1 configs are rejected with a clear migration error
- josh.monorepo_url is required; josh.monorepo_auth is optional (default https)
- mono_auth_url() in lib/auth.sh mirrors subrepo_auth_url()
- MONOREPO_API derives from monorepo_url's host instead of .[0].gitea_host;
  env-var override preserved as escape hatch
- initial_import() and force-push call mono_auth_url() instead of building URLs inline
- ADR-012 documents the rationale; CHANGELOG includes migration snippet

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,42 @@
 # Changelog
 
+## 2.0.0
+
+### Breaking Changes
+
+- **`schema_version: 2` is now required.** v1 configs are rejected with a migration pointer. Add `schema_version: 2` at the top of `.josh-sync.yml`.
+- **`josh.monorepo_url` is now required.** Set it to your monorepo's git clone URL — `git@host:org/repo.git` (SSH), `ssh://...`, or `https://host/org/repo.git`. Removes the silent inference of the gitea host from the first target's `subrepo_url`, which silently misbehaved when the monorepo and a target lived on different gitea instances. See [ADR-012](docs/adr/012-explicit-monorepo-url.md).
+- **`MONOREPO_API` derivation changed.** The default is now `https://{monorepo_url's host}/api/v1/repos/{monorepo_path}`. The env-var override is preserved as an escape hatch for custom API endpoints.
+
+#### Migration
+
+```yaml
+# Before (v1.x)
+josh:
+  proxy_url: "https://josh.example.com"
+  monorepo_path: "org/monorepo"
+
+# After (v2.0.0)
+schema_version: 2
+josh:
+  proxy_url: "https://josh.example.com"
+  monorepo_path: "org/monorepo"
+  monorepo_url: "git@gitea.example.com:org/monorepo.git"   # required
+  monorepo_auth: "ssh"                                       # optional, default "https"
+```
+
+If you previously set the `MONOREPO_API` env var to work around the first-target-host bug, you can remove it — the new derivation gets it right from `monorepo_url`.
+
+### Features
+
+- **Multi-host configs supported.** The monorepo and any subrepo may live on different gitea instances. Target ordering no longer affects how the monorepo's host is resolved.
+- **SSH clone of the monorepo via `monorepo_auth: ssh`.** Uses the user's ssh-agent / `~/.ssh/config`; no token required for the clone itself. PR creation still uses `GITEA_TOKEN`.
+- **Symmetric config shape.** Monorepo and subrepos now both declare a URL plus an auth method.
+
+### Fixes
+
+- First-target ordering no longer load-bearing on `MONOREPO_API` derivation (was `gitea_host=.[0].gitea_host` in v1.x).
+
 ## 1.5.0
 
 ### Breaking Changes