fix(ci): move workflow to .gitea/workflows — the server is Gitea, not Forgejo

The runner was alive all along (gitea/act_runner, ubuntu-latest label);
no run ever appeared because Gitea only reads .gitea/workflows/ (or
.github/workflows/) and ignores the .forgejo/ path the workflow shipped
under. The legacy repo's .gitea/workflows/check.yml was the clue.
References corrected (workflow header, TESTING.md, agent files); this
push doubles as the first live trigger of the workflow.

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

agent/BACKLOG.md

@@ -22,16 +22,18 @@ next, in what order*.
 
 ## NOW
 
-### 20. Confirm the Forgejo runner is alive `[human]`
-The checks-on-push workflow (`.forgejo/workflows/check.yml`) shipped;
-the repo has `has_actions: true` and the legacy `check.yml` ran 57
-times on an act_runner, but whether that runner still exists is not
-API-visible without auth. Check the first run of the new workflow at
-https://git.bemagri.xyz/bernardo/Nomarchy/actions — if it sits queued,
-re-register an act_runner (docker, `ubuntu-latest` label). **Stretch:**
-a second runner on a NixOS host with `/dev/kvm` (label `nix-kvm`) —
-then uncomment the workflow's `vm-checks` job and the VM suite + real
-builds run in CI too (that upgrades half of item 14 for free).
+### 20. Confirm the first CI run goes green `[human]`
+~~Runner registration~~ — resolved: the runner was alive all along
+(gitea/act_runner via docker-compose, `ubuntu-latest` label); the
+workflow was in `.forgejo/workflows/`, which **Gitea** ignores — moved
+to `.gitea/workflows/`. Remaining: watch the first real run at
+https://git.bemagri.xyz/bernardo/Nomarchy/actions — the eval job's
+container recipe is inherited from the legacy repo but this flake's
+eval is new territory (memory headroom of the runner container is the
+likely failure mode; the legacy repo OOM'd on heavy evals). **Stretch
+(unchanged):** a second runner on a host with `/dev/kvm` + nix (label
+`nix-kvm`, host mode) unlocks the workflow's commented `vm-checks` job
+— the VM suite + real builds in CI (upgrades half of item 14 free).
 
 ### 3. Memory-pressure protection (no more frozen desktops)
 New. A workstation that compiles from source *will* hit memory