git stack: switch provision-secrets to Pattern B .env rewrite (test phase) + add git to bootstrap-tier guard

Context: git hosts the source of truth for every other stack's compose
files, so in a disaster-recovery scenario it must be restorable from a
flat git.yaml + git.env backup alone, with zero dependency on a running
Swarm's Docker secret store (native Docker secrets can't be resolved
until Swarm already exists, which is the circular dependency git.yaml
would otherwise create). Path 2 (documented decision): Pattern B for
git specifically, same mechanism the ai stack already uses.

provision-secrets / git) case:
  - Previously created native Docker secrets (git_db_password,
    git_runner_token, git_mcp_access_token) via create-secrets.sh —
    leftover from an earlier, abandoned Pattern C attempt.
  - Now rewrites only the secret-bearing lines (GITEA__database__PASSWD,
    GITEA_RUNNER_REGISTRATION_TOKEN, GITEA_MCP_ACCESS_TOKEN) via
    grep -v + printf, mirroring the ai) case exactly. Also strips the
    legacy GITEA_ACCESS_TOKEN key name so the test file converges on the
    git.env.example-documented key.
  - TEST PHASE: target is git.env.pipelinetest, NOT git.env. The real
    git.env is never opened for writing by this step. First run seeds
    the test file from the real git.env (to carry over all non-secret
    lines), then only the 3 secret lines are refreshed on every push.
  - Real cutover (pointing git.yaml/stack-deploy at the generated file,
    then retiring git.env.pipelinetest) is a deliberate follow-up step
    after manually diffing the rendered output.

deploy / bootstrap-tier guard:
  - Added git to the traefik|woodpecker|postgresql|secrets guard list.
    git.yaml changes now sync to the host but require a manual
    `stack-deploy.sh git` run, same as the other foundational stacks —
    prevents an auto-deploy of a bad git.yaml change from taking down
    Gitea before a human can look at it (Gitea itself is what every
    other pipeline needs to trigger a fix).

.woodpecker/deploy.yml

@@ -221,10 +221,36 @@ steps:
               ssh -o StrictHostKeyChecking=no root@$${SWARM_MANAGER_IP} "source /tmp/cs.sh
                 create_or_update_secret 'gamma_auth_token' '$${GAMMA_AUTH_TOKEN}'";;
             git)
-              ssh -o StrictHostKeyChecking=no root@$${SWARM_MANAGER_IP} "source /tmp/cs.sh
-                create_or_update_secret 'git_db_password'       '$${GIT_DB_PASSWORD}'
-                create_or_update_secret 'git_runner_token'      '$${GIT_RUNNER_TOKEN}'
-                create_or_update_secret 'git_mcp_access_token'  '$${GIT_MCP_ACCESS_TOKEN}'";;
+              # PATTERN B, DELIBERATE (see decision notes) — git hosts the source
+              # of truth for every other stack's compose files, so it must be
+              # restorable from a flat git.yaml + git.env backup alone, with zero
+              # dependency on a running Swarm's Docker secret store. Native Docker
+              # secrets (Pattern C) can't satisfy that: they only exist inside an
+              # already-running Swarm, which is exactly the circular dependency
+              # this stack can't have. Mirrors the ai) case's grep -v + printf
+              # rewrite-in-place approach, never sed (values may contain slash,
+              # dollar sign, ampersand).
+              #
+              # TEST PHASE: target is git.env.pipelinetest, NOT the real git.env.
+              # The real file is never opened for writing by this step. First run
+              # seeds the test file from the real git.env (carries over all
+              # non-secret lines untouched); every push after that only refreshes
+              # the 3 secret lines below. Also strips the legacy GITEA_ACCESS_TOKEN
+              # key name so the test file converges on the git.env.example-
+              # documented GITEA_MCP_ACCESS_TOKEN key. Cutover to the real file —
+              # and pointing git.yaml/stack-deploy at it — is a deliberate,
+              # separate follow-up after manually diffing this render.
+              ssh -o StrictHostKeyChecking=no root@$${SWARM_MANAGER_IP} "FILE=/volume1/docker/compose-files/git.env.pipelinetest
+                TMP=\$FILE.tmp.\$\$
+                [ -f \$FILE ] || cp /volume1/docker/compose-files/git.env \$FILE
+                grep -vE '^(GITEA__database__PASSWD|GITEA_RUNNER_REGISTRATION_TOKEN|GITEA_MCP_ACCESS_TOKEN|GITEA_ACCESS_TOKEN)=' \$FILE > \$TMP 2>/dev/null || touch \$TMP
+                { cat \$TMP
+                  printf 'GITEA__database__PASSWD=%s\n' '$${GIT_DB_PASSWORD}'
+                  printf 'GITEA_RUNNER_REGISTRATION_TOKEN=%s\n' '$${GIT_RUNNER_TOKEN}'
+                  printf 'GITEA_MCP_ACCESS_TOKEN=%s\n' '$${GIT_MCP_ACCESS_TOKEN}'
+                } > \$FILE
+                rm -f \$TMP
+                echo '  [OK] git.env.pipelinetest updated - real git.env untouched'";;
             homeassistant)
               ssh -o StrictHostKeyChecking=no root@$${SWARM_MANAGER_IP} "source /tmp/cs.sh
                 create_or_update_secret 'homeassistant_frigate_rtsp_password' '$${HOMEASSISTANT_FRIGATE_RTSP_PASSWORD}'
@@ -352,7 +378,7 @@ steps:
 
           # Bootstrap-tier guard: file synced to host, deploy is MANUAL
           case "$STACK" in
-            traefik|woodpecker|postgresql|secrets)
+            traefik|woodpecker|postgresql|secrets|git)
               echo "  [BOOTSTRAP] $STACK: file synced. Deploy is MANUAL."
               echo "  Run: bash /volume1/docker/compose-files/deploy/stack-deploy.sh $STACK"
               continue ;;