T08 iter 3: GROUND modes, INVESTIGATE, SOLVE

Fills in resolution steps 1, 4 and 6 (GR-R06):

- GR-R05 mode choice: a player who revealed GROUND picks GR/OU/ND after
  Reveal. Resolution refuses to start while any revealed GROUND lacks a
  mode, and only that player may choose it.
- GR-A10 GROUND-GR: self -2 Stress and Freedom readied.
- GR-A01 INVESTIGATE: reveal the chosen hidden non-Denied Problem, then
  draw one Solution; the draw still happens when nothing is revealable.
- GR-A02 SOLVE: spend a Solution of the Problem's suit and claim it; a
  later resolver the same round spends nothing, per Lead order.
- GR-A13 tightened: INVESTIGATE must target a hidden Problem, SOLVE a
  face-up non-Denied one. Previously any existing Problem was accepted.

Deck exhaustion (U4) reshuffles the discard, seeded from the game seed
and round so validate stays a pure function of state. The resulting
order travels inside DeckReshuffled, so replay never re-derives it.

Still pending, each because it needs its own decision command rather
than a default: GROUND-OU and GROUND-ND three-way choices (GR-A11/A12)
and the DARVO stage machine (GR-D02..D07). No scenario claims coverage
of them.

Filler picks in existing scenarios moved from GROUND to INVESTIGATE:
GROUND now has a real Stress effect, which was polluting the Support
and Attack assertions.

11 scenarios pass, 34 rules covered; 17 tests, fmt/clippy green.

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

scenarios/ground/gr-d01-darvo-trigger.yaml

@@ -18,10 +18,10 @@ commands:
     args: { action: ATTACK, target: P2 }
   - actor: P2
     cmd: select_action
-    args: { action: GROUND }
+    args: { action: ATTACK, target: P3 }
   - actor: P3
     cmd: select_action
-    args: { action: GROUND }
+    args: { action: INVESTIGATE, problem: 3 }
   - actor: SYSTEM
     cmd: reveal
   - actor: SYSTEM