fix(adversaries): repair four of the five sparring bots

The user suspected these were bugged. They were, and the verdicts are not
uniform - three genuinely broken, one merely sloppy, one fine:

- WaveSurfer: GENUINELY BUGGED, worst of the five. (a) The enemy velocity
  decomposition was sin/cos SWAPPED - enemyVx used sin and enemyVy used cos,
  while Tank Royale is 0 deg = East, CCW+, so it must be cos for X and sin for
  Y. Its linear-prediction gun was aiming at a reflected position. (b) The wall
  escape flipped strafeDir on EVERY tick the bot was inside the wall margin,
  so instead of turning away it flip-flopped in place: measured standing still
  (speed < 0.5) for 96.2% of ticks with a longest continuous standstill of 1398
  ticks. Fixed with a hysteretic wall-escape selection plus a corner escape,
  dead enemyLastDir removed, and per-round state reset.
  AFTER, measured through the booter: rest 12.3%, mean speed 6.69, full speed
  79.7%, longest zero run 18, perpendicular 0.845 / radial 0.012 - it now
  actually strafes. Gun sanity: lead error 1.0 px vs 106 px for head-on on a
  constant-velocity target; lead gun 45.8% hits vs 29.3% for head-on.
- PatternMover: GENUINELY BUGGED. Real deadlock - it decremented its step
  counter by the REQUESTED amount while issuing setTargetSpeed(8), so against a
  wall the counter never reached 0, advanceStep never ran and it was stuck
  forever (309-tick standstill). Now counts down by ACTUAL distance/turn with a
  STALL_LIMIT watchdog and steers toward the arena centre. Standstill 309 -> 19
  ticks; full-speed ticks 10.0% -> 28.4%.
- OscillatorBot: GENUINELY BUGGED, milder. No wall handling at all, so it
  ground along walls 53.4% of ticks and could pin in a corner. Added wall
  steering that preserves the fixed 25-tick reversal cadence. Wall-band 53.4%
  -> 18.6%, mean wall distance 72 -> 119.
- RandomMover: merely sloppy, not broken. Its turn intent saturated against the
  speed-dependent limit (18.4% of moving ticks clamped) and the fire gate was a
  very loose 10 deg. Now clamps to calcMaxTurnRate and fires within 3 deg.
  Saturation 18.4% -> 3.9%.
- SittingDuck: FINE. Speed 0 for 100% of ticks, zero shots. Left untouched -
  it is a duck by design.

Adds test_wavesurfer_velocity.nim, a direct assertion that the decomposition is
cos/sin and explicitly NOT the swapped form (7 cases).

KNOWN ISSUE, not fixed: RandomMover/PatternMover/WaveSurfer import
tankroyale_botapi 1.0.1 and intermittently SIGSEGV in
tankroyale_botapi/event_queue.nim:89 addEvent, freezing the bot for the rest of
the battle. It reproduces on old and new code and never occurs for SittingDuck/
OscillatorBot, which import robocode_tankroyale_botapi 1.0.7. Migrating the
three to 1.0.7 would likely fix it and is worth doing - it is a real
reliability risk for these as sparring partners.

common_libs/test_framework/adversaries/OscillatorBot/src/OscillatorBot.nim

@@ -7,8 +7,10 @@ import tankroyale_botapi
 const botJsonPath = currentSourcePath().parentDir / "OscillatorBot.json"
 
 const
-  SPEED  = 7.0    # forward/backward speed
-  PERIOD = 25     # ticks between direction reversals
+  SPEED       = 7.0    # forward/backward speed
+  PERIOD      = 25     # ticks between direction reversals
+  TURN_RATE   = 4.0    # deg/tick zigzag turn
+  WALL_MARGIN = 60.0
 
 type OscillatorBot = ref object of Bot
   tickCount: int
@@ -33,13 +35,32 @@ method onScannedBot*(bot: OscillatorBot, e: ScannedBotEvent) =
 
 method run*(bot: OscillatorBot) =
   while isRunning():
+    # The reversal cadence is fixed and independent of walls: the zigzag period
+    # stays exactly PERIOD ticks.
     inc bot.tickCount
     if bot.tickCount mod PERIOD == 0:
       bot.moveSign *= -1.0
       bot.turnSign *= -1.0
 
     setTargetSpeed(bot.moveSign * SPEED)
-    setTurnRate(bot.turnSign * 4.0)
+
+    # Wall handling that preserves periodicity: when close to a wall, steer the
+    # actual movement direction (forward or backward, per moveSign) towards the
+    # arena centre instead of following the fixed zigzag turn.
+    let x      = getX()
+    let y      = getY()
+    let arenaW = getArenaWidth().float
+    let arenaH = getArenaHeight().float
+    let nearest = min(min(x, arenaW - x), min(y, arenaH - y))
+    if nearest < WALL_MARGIN:
+      let toCenter = directionTo(x, y, arenaW * 0.5, arenaH * 0.5)
+      let desired  = if bot.moveSign >= 0.0: toCenter
+                     else: normalizeAbsoluteAngle(toCenter + 180.0)
+      let delta = normalizeRelativeAngle(desired - getDirection())
+      setTurnRate(delta.clamp(-MAX_TURN_RATE, MAX_TURN_RATE))
+    else:
+      setTurnRate(bot.turnSign * TURN_RATE)
+
     setRadarTurnRate(45.0)  # spin radar to keep scanning
     go()