CB-WP-0008-T03: prove the 2-6 player range

GR-O01 states 2-6 players; every scenario in the corpus was 3-player.
Now all five counts play to GameEnded under both policies and reproduce
at the same seed, with scenarios at both boundaries and the CLI
transcript run at 2p, 3p and 6p.

Nothing broke — the rules are seat-count-generic. What the boundaries
exposed is arithmetic: with the standard preset's placeholder Problem
values (value = priority), the best total any game can reach is 3 at 2p,
6 at 3-4p, 10 at 5-6p, against GR-E01 thresholds of 5, 7 and 9. Group
success is unreachable below five seats regardless of play, and no
scenario noticed because none had played to scoring with everything
claimed.

GR-S01 calls the fixture a stand-in for scenario Problem data, so this
is evidence the stand-in is not neutral, not that GR-E01 is wrong. It is
pinned by a passing scenario, an arithmetic test, and a provisional
marker owned by ground-game so it ages in `make coverage`. The test
states its own delete-by: it is expected to fail when Problem values
become real data, and that failure is the signal to delete it.

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

scenarios/ground/gr-o01-six-player.yaml

@@ -0,0 +1,51 @@
+scenario: ground/gr-o01-six-player
+description: >
+  GR-O01's upper boundary, the counterpart to gr-o01-two-player. Six
+  seats exercise the 5–6p Problem set (GR-S01, four priorities) and the
+  longest resolution order (GR-R07, Lead first then clockwise with a
+  wrap).
+covers: [GR-O01, GR-S01, GR-R07]
+seed: 42
+setup:
+  players: 6
+  preset: standard-6p
+commands:
+  - actor: P1
+    cmd: select_action
+    args: { action: INVESTIGATE, problem: 2 }
+  - actor: P2
+    cmd: select_action
+    args: { action: INVESTIGATE, problem: 3 }
+  - actor: P3
+    cmd: select_action
+    args: { action: INVESTIGATE, problem: 4 }
+  - actor: P4
+    cmd: select_action
+    args: { action: SUPPORT, target: P5 }
+  - actor: P5
+    cmd: select_action
+    args: { action: GROUND }
+  - actor: P6
+    cmd: select_action
+    args: { action: ATTACK, target: P1 }
+  - actor: SYSTEM
+    cmd: reveal
+  - actor: P5
+    cmd: choose_ground_mode
+    args: { mode: GR }
+  - actor: P5
+    cmd: respond_to_support
+    args: { response: accept_bond }
+  - actor: SYSTEM
+    cmd: resolve
+  - actor: SYSTEM
+    cmd: end_round
+expect:
+  events:
+    - kind: ProblemRevealed
+    - kind: RoundEnded
+  state:
+    # GR-S01: four Problems at six players.
+    "problems.4.face_up": true
+    "round": 2
+  rejects: []