fix(gitea-ssh-hatchmate): correct account_ref space id (hatchmate, not platform)

The accelerators/ai-enablement precedent uses the literal 'platform' space
id — those credentials happen to live in the platform-owned CP accounts.
For hatchmate the credentials live in a CP account owned by the hatchmate
space, so the ref must be 'hatchmate.space:hatchmate'. Misnamed ref caused
the dispatcher's account resolver to fail with 'no active account for
AccountRef(name=hatchmate, scope=space:platform)', failing every review
task in the W4 vertical slice within seconds of dispatch.

After this lands and the next CRS sync (~5 min) refreshes the concepts
PVC, the next auto-advance fire on dfc4358c should resolve the account
and proceed through the working-repo clone with the per-org hatchmate key.

harnesses/contexts/gitea-ssh-hatchmate/v1/harness.yaml

@@ -23,6 +23,6 @@ scripts:
 
 secrets_required:
   - name: gitea-ssh-hatchmate
-    account_ref: "hatchmate.space:platform"
+    account_ref: "hatchmate.space:hatchmate"
     mount_path: /run/agent/secrets/gitea-ssh-hatchmate
     mode: "0400"