feat(forge-credential): add gitea-ssh-hatchmate/v1 layer + 4 hatchmate composite forks

M2-CRS W4 unblock: dispatched agents could not clone hatchmate/hatchmate-agents
because the shared gitea-ssh/v1 context mounts the ai_enablement deploy key,
which is scoped to skynet/* only. Same bug would hit every project whose
working repo lives outside the skynet org.

This implements the per-org pattern the framework already uses for accelerators
(gitea-ssh-accelerators/v1) and homelab (gitea-ssh-homelab/v1):

- harnesses/contexts/gitea-ssh-hatchmate/v1/{init.sh,harness.yaml} — NEW
  forge-credential context mirroring accelerators, with account_ref
  'hatchmate.space:platform' and write_targets covering hatchmate/*. The
  init.sh stages the ESO-mounted private key to ~/.ssh/gitea-oreillyit-nz-hatchmate
  (matching the ssh alias declared in harness.yaml). URL host pattern
  'gitea.oreillyit.nz-hatchmate' (per-org alias) drives SSH config block
  selection — already auto-written by harness_init.py from each layer's
  ssh_hosts: declarations.

- harnesses/composites/code-*-tdd-repo-hatchmate/v1/ — NEW composites for
  fable/minimax/airouter/opus that compose BOTH gitea-ssh/v1 (for reference
  clones, skynet org) AND gitea-ssh-hatchmate/v1 (for working-repo clone +
  push, hatchmate org). Composites are unchanged for non-hatchmate projects.

- tests/invariants/test_forge_credentials_declare_write_targets.py — the
  existing xfail(strict=True) marker was wrong: the 4 existing layers all
  declare write_targets today, so the test was XPASSing. Removed the
  xfail marker so HC-11 is now a real positive gate (5 layers instead
  of 4). This was a pre-existing test bug surfaced by the 5th layer.

W4 next step: dispatcher's account_ref resolution needs the hatchmate CP
account + grant to be created (via the new scripts/provision-hatchmate-fork-key.sh
in the hatchmate app repo).

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

@@ -0,0 +1,28 @@
+kind: context
+name: gitea-ssh-hatchmate
+version: 1
+description: "Gitea SSH: clone/push via SSH key for gitea.oreillyit.nz (hatchmate org — agent working-repo key for hatchmate/hatchmate-agents)"
+requires: []
+provides: [git-access]
+# HC-11: repos this layer's forge credential may push to (host-qualified; CRS-103 gate).
+write_targets:
+  - "gitea.oreillyit.nz/hatchmate/*"
+
+git_identity:
+  name: "agent-runtimes"
+  email: "agent@oreillyit.nz"
+
+ssh_hosts:
+  - alias: gitea.oreillyit.nz-hatchmate
+    hostname: gitea.oreillyit.nz
+    user: git
+    identity_secret: GITEA_SSH_KEY
+
+scripts:
+  init: "./init.sh"
+
+secrets_required:
+  - name: gitea-ssh-hatchmate
+    account_ref: "hatchmate.space:platform"
+    mount_path: /run/agent/secrets/gitea-ssh-hatchmate
+    mode: "0400"