chore(training): close Stage 5 by human override, re-derive its air-touch gate

productive_air_touch_episode_fraction's 0.02 floor was set as an explicit
PROVISIONAL guess (see the Round 10 comment in generation5.py) with
instructions to re-derive it from attempt 1's measured tail. That never
happened: five more Stage-5 attempts (20260824 through -retry4) ran against
the unchanged number, reading 0.00004/0.00006/0.00002/0.00018/0.00006 -- no
trend, ~500x under the floor -- while every other gate passed comfortably and
each attempt beat the Stage-4 reference head-to-head. Direct TensorBoard
query of retry4's full run confirms the touches are real and stable, just
rare (22/1000 rollout-logging windows registered one touch in the
~100-episode buffer), so further identical retries were not going to close a
500x gap.

Lowered the floor to 0.00002 (the minimum of the five measured attempts),
same as-under-the-observed-band logic the Stage-4 override used for
goal_rate. Flipped retry4's log entry to decision: pass with a
decision_override block (same pattern as the Stage-4 override) and advanced
generation5_state.json to Stage 6 attempt 0. Documented in TRAINING.md and
flagged Stage 6's own 0.015 floor for the same metric as equally unvalidated.

TRAINING.md

@@ -808,6 +808,51 @@ measure is visibly happening, check that the environment can produce the
 event at all before touching the reward function again. Cost of not checking
 here: three rounds and 360M timesteps.
 
+**The gate itself was wrong, and so was its bar (2026-08-24).** Retry2 —
+resumed under the fixed drill — still logged `productive_air_touch_fraction`
+at 0.0. Three findings, each measured rather than argued: (1)
+`productive_air_touch_fraction` divides by *total* touches, so Stage 4's own
+success at ground handling dilutes an unchanged aerial rate toward zero;
+replaced with `productive_air_touch_episode_fraction` (did *this episode*
+contain a productive aerial touch at all). (2) `AIR_TOUCH_HEIGHT` (5 m) was
+never derived from anything — normal match play put the ball's mean altitude
+at ~1.6 m and its average episode peak at only ~2.4 m, clearing 5 m barely 5%
+of the time — so it was lowered to 3.0, this project's existing airborne
+threshold, with `_place_air_intercept`'s band retuned 8-14m → 6-10m to match
+(simulated against real physics this pair strictly dominates the old one: 68%
+reach vs 53%, 57% above-bar touches vs 41%). (3) the policy could not climb
+at all and the entropy controller could not see it — its target summed over
+action heads while `thrust_y` alone sat starved at 14% of its own ceiling,
+leaving the ship in free fall ~84% of the time. Fixed with
+`--min-head-entropy-frac` (any one starved head raises `ent_coef`) and a
+raised `--ent-coef-max`. Resumes retry2 rather than restarting, on narrower
+grounds than the drill fix above: the changed term (`AIR_TOUCH_HEIGHT` now
+gates `air_touch_bonus_weight`'s payout) had never once fired in nine
+attempts, so there was no learned expectation about it for retry2's
+checkpoint to carry.
+
+**Stage 5 closed by human override on 2026-08-29**, not the automatic gate,
+after five more attempts (2026-08-24 to 2026-08-28) under the Round 10 fixes.
+`productive_air_touch_episode_fraction` read 0.00004, 0.00006, 0.00002,
+0.00018, 0.00006 across them — no trend toward the 0.02 floor, just noise at
+the same order of magnitude — while every other gate passed comfortably on
+every attempt and each one beat the Stage-4 reference head-to-head (the last,
+`-retry4`: goal_rate 0.796 vs 0.72, upright 0.778 vs 0.40, forward_motion
+0.493 vs 0.20, eval 53-26-21 with balanced sides 29-11 / 24-15).
+`rollout/air_touch_fraction` over that attempt's full run confirmed the
+touches are real, just rare: 22 of 1000 rollout-logging windows registered
+exactly one aerial touch in the ~100-episode SB3 buffer. The 0.02 floor was
+always PROVISIONAL — the comment that set it said explicitly to re-derive it
+from attempt 1's tail, which never happened across the five retries. Lowered
+to 0.00002, the minimum of the five measured attempts, the same "just under
+the observed band" logic the Stage-4 override above used for `goal_rate`.
+`generation5_state.json` has `-retry4`'s log entry `decision` flipped to
+`"pass"` with a `decision_override` block, `stage_index`/`attempt`/`status`
+advanced to Stage 6 attempt 0. Stage 6's own `0.015` floor for the same
+metric carries the identical unvalidated-guess problem and has never run a
+single attempt — re-derive it from measured data once Stage 6 produces a
+real tail, the same way this one now has been.
+
 Stage 6's `league` opponent mode samples a historical exported policy at each
 episode reset. Each later stage preserves the preceding shaping and adds one
 new difficulty.