feat(job): wire use-git-clone + submodules; default in-guest clone

The job command previously discarded --use-git-clone and --submodules
(`del`) and always in-guest cloned with submodules off — making both
action inputs dead no-ops (submodule repos silently broken).

- job.py: --use-git-clone/--host-clone and --submodules/--no-submodules
  are real booleans defaulting to ON. Default = in-guest clone with
  submodules. --host-clone clones on the host into a temp dir
  (_host_clone) and transfers a zip; temp dir cleaned in finally.
  clone_submodules now honoured (was hardcoded False).
- action.yml: use-git-clone / submodules default 'true'; forward the
  explicit positive/negative flag so the Python default is overridden
  deterministically.
- self-test.yml: add smoke-{windows,linux}-hostclone jobs covering the
  host-side transport (default jobs already cover in-guest).
- tests: default-transport, host-clone, and --no-submodules coverage.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitea/actions/local-ci-build/action.yml

@@ -48,9 +48,10 @@ inputs:
 
   submodules:
     description: >
-      Set to "true" to clone the repository with --recurse-submodules.
+      Recurse submodules when cloning. Default "true". Set to "false"
+      to skip submodule init/update.
     required: false
-    default: 'false'
+    default: 'true'
 
   guest-os:
     description: >
@@ -61,12 +62,14 @@ inputs:
 
   use-git-clone:
     description: >
-      Set to "true" to clone the repository inside the VM rather than
-      transferring a zip from the host. Requires Git in the template (see
-      Install-CIToolchain-WinBuild2025.ps1 Step 12 / Install-CIToolchain-Linux2404.sh).
-      Preferred for repositories larger than ~200 MB.
+      Transport for the repo source. Default "true": clone inside the
+      build VM (requires Git in the template — see
+      Install-CIToolchain-WinBuild2025.ps1 Step 12 /
+      Install-CIToolchain-Linux2404.sh). Set to "false" for the
+      host-side variant: the host clones the repo and transfers a zip
+      to the guest (useful when the guest cannot reach Gitea).
     required: false
-    default: 'false'
+    default: 'true'
 
   configuration:
     description: >
@@ -269,8 +272,13 @@ runs:
             '--snapshot-name',         $resolvedSnapshotName
         )
 
-        if ($env:INPUT_SUBMODULES       -eq 'true') { $pyArgs += '--submodules' }
-        if ($env:INPUT_USE_GIT_CLONE    -eq 'true') { $pyArgs += '--use-git-clone' }
+        # Submodules and transport default to ON; pass the explicit
+        # negative flag when the caller opted out so the Python default
+        # (also ON) is overridden deterministically.
+        if ($env:INPUT_SUBMODULES -eq 'false') { $pyArgs += '--no-submodules' }
+        else { $pyArgs += '--submodules' }
+        if ($env:INPUT_USE_GIT_CLONE -eq 'false') { $pyArgs += '--host-clone' }
+        else { $pyArgs += '--use-git-clone' }
         if ($env:INPUT_USE_SHARED_CACHE -eq 'true') { $pyArgs += '--use-shared-cache' }
         if ($env:INPUT_SKIP_ARTIFACT    -eq 'true') { $pyArgs += '--skip-artifact' }
         if ($env:INPUT_EXTRA_GUEST_ENV_JSON -and $env:INPUT_EXTRA_GUEST_ENV_JSON -ne '{}') {