workflows: use x-access-token for git clone (Gitea-compatible)

The hardcoded "forgejo-runner" username worked on Forgejo because its
runner accepted any user when the password is a valid GITHUB_TOKEN.
Gitea's act_runner v0.6+ rejects unknown usernames with:
  remote: Failed to authenticate user
  fatal: Authentication failed for 'https://git.okcu.io/.../...'

x-access-token is the canonical "the password IS the token" username
on GitHub Actions and works equally on Gitea, Forgejo and gitea.com.

Run that surfaced the issue: gitea run #1, task 1, sha 0f63f15,
"Cloning into '/tmp/src'... remote: Failed to authenticate user".

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

.gitea/workflows/build.yml

@@ -29,7 +29,7 @@ jobs:
     steps:
       - name: Checkout
         run: |
-          git clone --no-checkout "https://forgejo-runner:${GITHUB_TOKEN}@git.okcu.io/${GITHUB_REPOSITORY}.git" /tmp/src
+          git clone --no-checkout "https://x-access-token:${GITHUB_TOKEN}@git.okcu.io/${GITHUB_REPOSITORY}.git" /tmp/src
           git -C /tmp/src checkout "$GITHUB_SHA"
           cp -a /tmp/src/. .
       - name: Vet
@@ -48,7 +48,7 @@ jobs:
     steps:
       - name: Checkout
         run: |
-          git clone --no-checkout "https://forgejo-runner:${GITHUB_TOKEN}@git.okcu.io/${GITHUB_REPOSITORY}.git" /tmp/src
+          git clone --no-checkout "https://x-access-token:${GITHUB_TOKEN}@git.okcu.io/${GITHUB_REPOSITORY}.git" /tmp/src
           git -C /tmp/src checkout "$GITHUB_SHA"
           cp -a /tmp/src/. .
       - name: Cross-compile drover.exe (windows/amd64)

.gitea/workflows/release.yml

@@ -18,7 +18,7 @@ jobs:
     steps:
       - name: Checkout
         run: |
-          git clone --no-checkout "https://forgejo-runner:${GITHUB_TOKEN}@git.okcu.io/${GITHUB_REPOSITORY}.git" /tmp/src
+          git clone --no-checkout "https://x-access-token:${GITHUB_TOKEN}@git.okcu.io/${GITHUB_REPOSITORY}.git" /tmp/src
           git -C /tmp/src checkout "$GITHUB_SHA"
           cp -a /tmp/src/. .