chore: fix rclcpp version

[iwatake2222]

Description

• Use a commit hash instead of a branch name for rclcpp.

Background

• Pilot.Auto uses a customized version of launch_ros, which depends on a modified rclcpp.
  • feat(load_composable_nodes): retry if no response after waiting 30 seconds when loading node launch_ros#36
  • feat(rclcpp_components): deduplicate node loading if FQN already exists rclcpp#12
• These changes were recently reverted by feat(rclcpp_components): change load_node service QoS to prevent failure on loading composable node. rclcpp#14, and the same revert will be applied to the t4-main-caret branch via feat(rclcpp_components): change load_node service QoS to prevent failure on loading composable node for caret branch rclcpp#15
• However, older versions of Pilot.Auto still rely on the customized launch_ros, so a pre-revert version of rclcpp must be used.

	launch_ros	rclcpp	Result
(~2026/1/13) Pilot.Auto w/ and w/o CARET	customized	customized	OK
(2026/1/13~) Pilot.Auto w/o CARET	reverted	reverted + QoS modified	OK
(2026/1/13~) Pilot.Auto(older version) w/ CARET without this PR	customized	reverted + QoS modified (t4-main-caret branch)	Incompatible
(2026/1/13~) Pilot.Auto(newer version) w/ CARET without this PR	reverted	reverted + QoS modified (t4-main-caret branch)	OK
(2026/1/13~) Pilot.Auto(older version) w/ CARET with this PR	customized	customized (4a026d54)	OK
(2026/1/13~) Pilot.Auto(newer version) w/ CARET with this PR	reverted	customized (4a026d54)	OK

Related links

Notes for reviewers

• This change will be reverted in the future when Pilot.Auto doesn't rely on a customized version of launch_ros
• or, we can move on a new version of CARET (v0.7.0)

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[iwatake2222]

@interimadd
Could you review this PR?
I just use a commit hash instead of a branch name for rclcpp. So that , the appropriate tier4/rclcpp is used in case Pilot.Auto uses tier4/launch_ros (especially the older version of Pilot.Auto)

[interimadd]

Thank you for your quick handling.