Add closed-loop simulator sketch + physics library (Router)

[toprakcelikel]

Add closed-loop simulator sketch + shared physics library (Router)

Summary

Router-side closed-loop simulator and the shared integer physics engine, split
out from #15 so the closed-loop sketch can be reviewed and merged on its own.

Restores the CAN backbone that PR #12 (full-sim-loop) introduced and PR #14
(modify stage 1 and 3) inadvertently dropped.

What's included

• Non_grapic_simulator/simulator_closed_loop/simulator_closed_loop.ino —
  Router-side closed-loop variant that reads real DBW inputs (throttle, brake,
  steering) and publishes pose / heading / speed / actual wheel angle as CAN
  frames (0x4C0, 0x4E0, 0x4F0, 0x430) for Sensor Hub Nav and DBW's
  steering PID to consume. Closes the Nav → DBW → Router → Nav loop.
• Non_grapic_simulator/libraries/simulator_physics/ — shared integer-only
  physics engine extracted into a small in-repo Arduino library
  (computeSpeed, updateAngle, updatePosition, sin1000/cos1000,
  wheel-pulse + angle-sensor output). Both sketches #include <simulator_physics.h>
  so future physics changes happen in one place.
• Non_grapic_simulator/README.md — describes the two simulator sketches and
  the shared physics engine, plus IDE setup/troubleshooting.
• .gitignore — ignore build/IDE artifacts.
• simulator_stage1.ino — only changes are the #include line + a SETUP
  banner; runtime behavior is identical to PR Fix #define comments and update brake model #14.

Notable changes

• Removed the Stage 2 ASCII command pipe and Stage 3 binary telemetry from
  the closed-loop sketch. Those were an in-sketch PC→Router command-injection
  path; the closed loop is now driven purely by DBW's pins and the CAN bus. All
  command-injection/test plumbing is consolidated into the upcoming
  test-automation PR (avoids two competing command paths).

• Fixed brake detection. Previously the Router inferred the brake from
  throttle level:

  bool brakeOn = (throttle < MIN_EFFECTIVE_THROTTLE);

  At low cruise speeds (e.g. Nav commanding ~100 cm/s) DBW's throttle PID can sit
  below MIN_EFFECTIVE_THROTTLE during ramp-up, which falsely engaged the brake
  and stalled the vehicle (~30 s stuck at waypoint 1). The Router now reads DBW's
  actual brake wire (DBW D44 → Router D48):

  int brakePinRaw = digitalRead(BRAKE_ON_PIN);
  bool brakeOn = BRAKE_ON_ACTIVE_LOW ? (brakePinRaw == LOW)
                                     : (brakePinRaw == HIGH);

  Adds a BRAKE_ON_ACTIVE_LOW config (default true for the Bridge's active-low
  relay wiring; flip to false for active-high wiring) and a B= field in the
  debug line for live visibility.

One-time setup (per developer)

Arduino IDE → File → Preferences → Sketchbook Location → set to
<repo>/Non_grapic_simulator. This lets the IDE find the shared
simulator_physics library. Full setup + troubleshooting in
Non_grapic_simulator/README.md.

Verification

• Flashed to the Router; closed loop runs and the vehicle moves correctly at low
  cruise speed (previously stalled ~30 s at waypoint 1).
• DBW continues to actuate — Router motion is derived from DBW's throttle/brake/
  steer output pins, so motion confirms DBW participation.

Out of scope (follow-up PR)

• NavigateTestRunner gateway, tools/test_runner.py, test CSVs, and assertion
  design notes.
• Reconciling the test-command interface with Folsom's merged Simulator.ino
  design.

Notes for reviewers

• Integer-only arithmetic throughout (no floating point), per project constraint.
• If the brake ever reads inverted on different wiring, flip BRAKE_ON_ACTIVE_LOW.
• Commits: closed-loop sketch + physics lib (30bcffd) → Stage 2/3 removal
  (8da87c0, cherry-picked) → Router brake fix.