feat(ModularBot): pluggable bot with 4 guns, phantom meteor movement, radar harness

- Gun harness: virtual bullet tracker, rolling fitness, auto-selector
- Guns: head-on, linear (extrapolation), circular (integrated formula), tsetlin machine (learning)
- Movement: phantom meteor gravity engine (danger histograms, phantom bullets, fire detection)
- Radar: harness + radar_lock adapter
- Color-coded modules: turret/bullet color per gun, body per movement, scan per radar
- Beats Target, SpinBot, Crazy, TrackFire in 10-round battles

common_libs/gun_harness/gun_interface.nim

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+## Gun harness — shared types and Gun concept.
+## Coordinate system: 0° = East, CCW positive (Tank Royale standard).
+## Bullet speed formula: 20 - 3 * power.
+
+import std/math
+
+const BotRadius* = 18.0  ## hit detection radius in px
+
+type
+  WorldState* = object
+    ## All raw data given to every gun every tick.
+    # Enemy
+    enemyX*, enemyY*:         float
+    enemySpeed*, enemyHeading*: float
+    # Self
+    selfX*, selfY*:           float
+    selfSpeed*, selfHeading*: float
+    selfRadarHeading*:        float
+    selfEnergy*:              float
+    enemyEnergy*:             float
+    # Arena
+    arenaWidth*, arenaHeight*: float
+    # Meta
+    tick*:                    int
+
+  GunPrediction* = object
+    ## Absolute (x, y) where the gun predicts the enemy will be.
+    x*, y*: float
+
+  FeedbackEvent* = object
+    ## Outcome of a resolved virtual bullet.
+    prediction*:  GunPrediction
+    bulletPower*: float
+    missDistance*: float  ## px; < BotRadius = hit
+    hit*:         bool
+
+proc bulletSpeed*(power: float): float {.inline.} =
+  20.0 - 3.0 * power
+
+## Gun concept — any type T implementing these two procs is a valid gun.
+template isGun*(T: typedesc): bool =
+  compiles(
+    block:
+      var g: T
+      let ws = WorldState()
+      let p: GunPrediction = g.predict(ws, 0.0)
+      let fe = FeedbackEvent()
+      g.onResult(fe)
+  )