fix(08-01): probe runs-on ubuntu-latest — runner has no self-hosted label

The act_runner advertises ubuntu-latest/ubuntu-24.04/ubuntu-22.04; runs-on:
self-hosted matched no runner and the probe job stayed queued. Switch the
probe (and the plan key-link) to ubuntu-latest. ci.yml (Plans 02-04) must
use the same label.

.gitea/workflows/runner-probe.yml

@@ -17,7 +17,9 @@ on:
 jobs:
   probe:
     name: runner-probe
-    runs-on: self-hosted
+    # Runner advertises ubuntu-latest/ubuntu-24.04/ubuntu-22.04 (no 'self-hosted' label).
+    # Probe confirmed `runs-on: self-hosted` matched no runner and the job stayed queued.
+    runs-on: ubuntu-latest
 
     # P-05: Service container — probe whether it spawns and on which hostname.
     # Uses healthcheck.sh --connect --innodb_initialized.

.planning/phases/08-gitea-ci/08-01-PLAN.md

@@ -32,9 +32,9 @@ must_haves:
       contains: "runner-probe"
   key_links:
     - from: ".gitea/workflows/runner-probe.yml"
-      to: "self-hosted runner"
+      to: "the registered act_runner"
-      via: "runs-on: self-hosted, on: push to gsd/phase-08-gitea-ci"
+      via: "runs-on: ubuntu-latest (runner has no self-hosted label), on: push to gsd/phase-08-gitea-ci"
-      pattern: "runs-on:\\s*self-hosted"
+      pattern: "runs-on:\\s*ubuntu-latest"
 ---
 
 <objective>