TFIL: time-indexed bullet heat (TR_TFIL_HEAT_TIME, DEFAULT OFF)

Make danger a function of time-to-arrival instead of flat distance. Bullet
core/aura/corridor heat becomes magnitude(power) * decay(dt), dt = along/speed:

  * decay(dt) = exp(-dt/tau) is a function of TIME; a fixed tau projects a
    pixel reach of speed*tau, so fast/weak bullets get a longer slope and slow
    ones a shorter one — derived from speed = 20 - 3*power, not hand-tuned.
    tau = TR_TFIL_HEAT_TAU.
  * magnitude(power) scales the near-end heat with power from DAMAGE
    (calcBulletDamage = 4p, linear in p; SCORE_PER_BULLET_DAMAGE = 1.0). Hit
    probability is FLAT across power (docs/env_reference.md), so risk does not
    justify power scaling — the cost of the hit does. Floored at 1.0 so a weak
    bullet's near end is never less dangerous than the flat model.
    Gain = TR_TFIL_HEAT_POWER_GAIN.

Every source is already f(dt), so the time-indexed planner (evaluate a cell at
the tick the bot would ARRIVE, i.e. heatDecay(dt - arrivalDelay)) is a one-line
change. It is intentionally NOT implemented here.

Default path is byte-identical: with TR_TFIL_HEAT_TIME unset both factors are
exactly 1.0 (IEEE x*1.0 is exact), and the committed golden replay in
common_libs/tests/test_tfil_commit_env.nim (20,026 ticks) still passes
byte-for-byte against the pre-change mover. The debug corridor outline is also
drawn only to the model's reach when enabled, so the GUI shows the shortening.

Offline field measurement (common_libs/tests/measure_tfil_heat_time.nim,
46,054 fixture ticks, tau=9/gain=1): corridor reach drops from 443px
wall-to-wall to 143px mean (32% retained); fraction of tiles > 10 goes
0.61 -> 0.57; largest contiguous safe region 118 -> 140 tiles; mean
distance-to-nearest-safe-tile 49 -> 42px. Saturation stays high because wall
radiance + pillar alone are 44% of tiles over threshold and are untouched.

Registers the three knobs in env_report (report + known-name set).

ModularBot_garage/src/env_report.nim

@@ -251,6 +251,11 @@ proc printEffectiveValues(ctx: EnvReportContext) =
   emit("TR_TFIL_COMMIT_TICKS", $TfilCommitTicks, sourceOf("TR_TFIL_COMMIT_TICKS"))
   emit("TR_TFIL_NO_REV", onOff(TfilNoRev), sourceOfPresence("TR_TFIL_NO_REV"))
   emit("TR_TFIL_COMMIT_LOG", TfilCommitLogPath, sourceOfPresence("TR_TFIL_COMMIT_LOG"))
+  # time-indexed bullet heat (default off = shipped flat model)
+  emit("TR_TFIL_HEAT_TIME", onOff(TfilHeatTime), sourceOf("TR_TFIL_HEAT_TIME"))
+  emit("TR_TFIL_HEAT_TAU", $TfilHeatTau, sourceOf("TR_TFIL_HEAT_TAU"))
+  emit("TR_TFIL_HEAT_POWER_GAIN", $TfilHeatPowerGain,
+       sourceOf("TR_TFIL_HEAT_POWER_GAIN"))
 
   # ── ramming ───────────────────────────────────────────────────────────────
   emit("TR_RAM_OPPORTUNITY", onOff(RamOppEnabled), sourceOf("TR_RAM_OPPORTUNITY"))
@@ -398,6 +403,7 @@ proc knownEnvNames*(): seq[string] =
     "TR_TFIL_RANGE_K", "TR_TFIL_CORRIDOR_HEAT", "TR_TFIL_WALL_HOTNESS",
     "TR_TFIL_TILE_REPLAN", "TR_TFIL_COMMIT_TICKS", "TR_TFIL_NO_REV",
     "TR_TFIL_COMMIT_LOG",
+    "TR_TFIL_HEAT_TIME", "TR_TFIL_HEAT_TAU", "TR_TFIL_HEAT_POWER_GAIN",
     # harness vars (read by the test framework, inherited by the bot, so they
     # must NOT be reported as typos)
     "TR_SERVER_JAR", "TR_BATTLE_RUNNER", "TR_BATTLE_RUNNER_DIR",