ci(integration): print the runner facts that rules 79 and 81 assert (#3237)

Three conditional rules state facts about this act_runner — services are
not reachable by hostname (79), the service container's name is derived
from the job's truncated display name (80), and `run:` steps execute
under a shell without bash features (81). None had ever been verified,
because each check reads "add a step to a live CI job and read the log"
and nobody wants to arrange a throwaway run to do it.

So the step is not throwaway. Two lines on every integration run turn the
next sweep of these rules into a log read. Rule 80 needs nothing new: the
container listing the suite step already prints for the name filter is
its evidence, and run 5055's log already answers it.

Every command is guarded with a fallback. This observes the lane; it must
not be able to break it.

.forgejo/workflows/ci.yml

@@ -279,6 +279,21 @@ jobs:
         env:
           UV_PROJECT_ENVIRONMENT: /opt/venv
         run: uv sync --locked --extra dev
+      # Standing answers to the checks carried by rules 81 and 79 — two facts
+      # about THIS runner that conditional rules assert as fact, and that
+      # otherwise need a throwaway job to confirm (#3237). Printing them on
+      # every integration run makes the next rulebook sweep a log read.
+      # Rule 80's evidence is the container listing the next step already
+      # prints. Every command is guarded: a diagnostic that can break the lane
+      # it observes is worse than no diagnostic.
+      - name: Runner facts (rules 79 and 81)
+        run: |
+          echo "--- rule 81: which shell runs a run: step ---"
+          readlink -f /bin/sh || echo "/bin/sh: not a symlink"
+          ps -p $$ -o comm= || true
+          echo "--- rule 79: is a service reachable by its hostname yet? ---"
+          getent hosts postgres \
+            || echo "no — 'postgres' does not resolve; the bridge-IP lookup is still required"
       - name: Integration suite (resolve service IP, migrate, test)
         run: |
           set -eux