oomwoo_sim_support: fix initialpose_pub sim-clock race

self.start was captured in __init__, where get_clock().now() can read 0
under use_sim_time (no /clock yet). Every _elapsed() then returned the
absolute sim time, so when the node starts against an already-running sim
(elapsed > timeout_sec) it fired the fail-open and exited WITHOUT ever
seeding /initialpose -- AMCL never localized, no map->odom. Baseline
self.start on the first tick instead, once the clock is running. Verified:
elapsed now reads real seconds (localize at ~3s) instead of 44s/270s.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: kaiaai

src/oomwoo_sim_support/oomwoo_sim_support/initialpose_pub_node.py

@@ -60,7 +60,11 @@ def __init__(self) -> None:
 
         self.localized = False
         self.reseeds = 0
-        self.start = self.get_clock().now()
+        # Captured on the first tick, not here: under use_sim_time get_clock()
+        # can read 0 at construction (no /clock yet), which would make every
+        # _elapsed() look like the absolute sim time and trip the fail-open
+        # before we ever seed. Baseline once the clock is actually running.
+        self.start = None
 
         self.pub = self.create_publisher(
             PoseWithCovarianceStamped, 'initialpose', 10)
@@ -93,6 +97,10 @@ def _seed(self) -> None:
         self.pub.publish(msg)
 
     def _tick(self) -> None:
+        if self.start is None:
+            # clock is running now; baseline elapsed from here
+            self.start = self.get_clock().now()
+            return
         el = self._elapsed()
         if self.localized:
             self.get_logger().info(