improvement: add bb_pid_controller.install igniter task

[jimsynz]

Summary

Adds an Igniter installer that scaffolds a PID controller in the robot module with runtime-tunable gains.

Running mix igniter.install bb_pid_controller will:

• Add a BB.PID.Controller entry to the robot's controllers section, with kp/ki/kd referencing :config.<name>.{kp,ki,kd} so the gains can be retuned at runtime through the BB parameter system without recompiling
• Define the :config.<name> param group with :kp, :ki, :kd (defaults 1.0 / 0.0 / 0.0)
• Import the package's formatter rules
• Print a notice reminding the user to fill in the [:TODO] topic paths once they know which joint to control

The topic paths (setpoint/measurement/output) are scaffolded as [:TODO] placeholders because the installer can't infer the joint paths from the robot topology.

Options

Flag	Default	Purpose
--robot / -r	{AppPrefix}.Robot	Robot module to target
--name / -n	pid	Controller name and param group name

Run the installer multiple times with different --name values to scaffold multiple PID loops.

Other changes

• Bumps bb to ~> 0.15.3 (for the new BB.Igniter helpers from improvement: add BB.Igniter helpers for add-on installers bb#86).
• Adds :mix to the dialyzer PLT so the use Mix.Task fallback in the installer typechecks cleanly.

Test plan

• mix check --no-retry passes
• 8 new unit tests covering controller, param group, custom names, formatter import, TODO notice, and idempotency
• All 28 tests pass