CB-WP-0025 T06/T07: a difficulty baseline that reports its own confound

T06. games/ground/examples/difficulty.rs, make difficulty, wired into make
self-tests, and a report file in ground-game under GROUND-WP-0005 with a
hub message pointing at it.

THE REPORT OPENS WITH THE RETRACTION, because what this task was written
to send was withdrawn by T02 and GROUND-WP-0005 is blocked on exactly that
number. They are told, in the first section, that we nearly sent them "the
game is too easy at 5-6 seats" and why it was wrong.

  seats  winnable  greedy  random  first-legal  spread
   2p      60%     60.0%    5.0%      76.7%      71.7
   3p      93%     88.3%    6.7%      25.0%      81.7
   4p     100%     93.3%    6.7%      30.0%      86.7
   5p     100%    100.0%    3.3%       0.0%     100.0
   6p     100%    100.0%    3.3%       0.0%     100.0

SPREAD justifies the whole redesign: 71.7 to 100.0 points between three
trivial policies. The table now shows why no single rate is a difficulty
rather than asserting it.

And the 5-6 rows point the OPPOSITE way from the withdrawn claim --
first-legal 0% against greedy 100% is the widest spread in the table,
which suggests play matters MORE there, not less. Neither reading is
established and the report says so.

The confound is stated in the tool's own output, not only in prose:
`winnable` is conditioned on greedy's play up to the final round, because
searching from round 1 is unaffordable. Presenting it as a property of the
deal would repeat this pass's error in a subtler form -- which is exactly
how a corrected project reintroduces a defect. NO THRESHOLD CHANGES ARE
PROPOSED.

The instrument can fail (spec §5): a witness must replay to a win, an
unwinnable position must report searched-out rather than a budget cut, a
one-node budget must not claim exhaustion, and the policy panel must
actually disagree. difficulty-baseline.rs marked superseded, kept as the
survey's dated snapshot. Registered as F16, inconsistent / withdrawn.

T07. evidence/CB-EV-0024. Five of nine defects came only from the review;
four from execution, and all four of those were in work written after it.
The wrong-denominator family now has five instances and still no control
-- facts-check catches copies that disagree, nothing catches a number
computed correctly against the wrong base. Tier L was an over-declaration
(no port, structurally M) and paid for itself anyway, because the review
is L-only. Chaos window 2 will close with zero overrides, making its
retirement condition untestable.

Named as open rather than implied done: the witness is NOT wired to the
ending page. The search works; the browser cannot ask it yet.

make all: exit 0. loop-lint clean.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Makefile

@@ -125,6 +125,7 @@ self-tests:
 	$(PY) $(TOOLS)/runtime-metrics.py --self-test
 	$(PY) $(TOOLS)/replay-test.py --self-test
 	$(PY) $(TOOLS)/design.py --self-test
+	cargo run --release -q -p games-ground --example difficulty -- --self-test
 	$(PY) $(TOOLS)/edition-check.py --self-test
 
 # T01 positive control: prove the environment fix, do not assume it. Runs
@@ -160,6 +161,12 @@ facts-check:
 facts-gen:
 	$(PY) $(TOOLS)/facts.py --gen
 
+# CB-WP-0025 T06: the difficulty table (specs/RetrospectiveAnalysis.md §4).
+# Winnable fraction from the solver plus a PLURAL policy panel -- a single
+# policy's win rate may not be reported as a difficulty (§4.1).
+difficulty:
+	@cargo run --release -q -p games-ground --example difficulty
+
 # CB-WP-0022 T05: the design-finding register, reported over
 # specs/GroundRules.md. Shows the QUEUE by default; the log of closed
 # findings is a line, not a listing, because a default view that mixes