feat(progression): capabilities the adapters need (commit A of the swap)

no behaviour change - additive only.

GrantSkill: pickups are free unlocks, and collecting one already owned is
a no-op rather than a free upgrade.
RevokeSkill: for skills that consume themselves (brick shield).
AbandonAttempt: leaving a level without dying, so no life is charged.

ApplyCheat rewrites the Playthrough through its snapshot rather than via
SetLives/AddCoins mutators, which ADR-0005 rules out - a bare mutator is
an invitation, and the old code had two paths to exactly that. Every
value is re-validated on the way back in and a rejected cheat leaves the
Playthrough untouched, which is asserted.

73 tests.

progression.tests/ProgressionServiceTests.cs

@@ -230,6 +230,71 @@ public class ProgressionServiceTests
         Assert.False(service.CanEnter(Second));
     }
 
+    [Fact]
+    public void A_collected_skill_is_granted_free_and_only_once()
+    {
+        // Skill pickups are not purchases — no coins change hands. Collecting one you already own is
+        // a no-op rather than a free upgrade.
+        var service = ServiceWithSkills();
+        service.RecordCoinsFound(Coins.Of(10));
+
+        Assert.True(service.GrantSkill(BrickThrow));
+        Assert.Equal(SkillLevel.First, service.LevelOf(BrickThrow));
+        Assert.Equal(Coins.Of(10), service.TotalCoins);
+
+        Assert.False(service.GrantSkill(BrickThrow));
+        Assert.Equal(SkillLevel.First, service.LevelOf(BrickThrow));
+    }
+
+    [Fact]
+    public void A_revoked_skill_is_gone_from_both_the_attempt_and_the_playthrough()
+    {
+        // BrickShieldSkillComponent consumes itself when broken, so this is gameplay rather than a cheat.
+        var campaign = TwoLevels();
+        var store = new InMemoryPlaythroughStore();
+        var service = new ProgressionService(
+            Profile.Empty(), store, new InMemoryProfileStore(), campaign, Skills(), Lives.Of(3));
+        service.StartPlaythrough(Id);
+        service.EnterLevel(First);
+        service.GrantSkill(BrickThrow);
+        service.FinishLevel(LevelTime.Of(10.0));   // commits it to the Playthrough
+        service.EnterLevel(Second);
+
+        service.RevokeSkill(BrickThrow);
+
+        Assert.False(service.IsOwned(BrickThrow));
+    }
+
+    [Fact]
+    public void Abandoning_an_attempt_discards_it_without_costing_a_life()
+    {
+        var service = ServiceWithSkills();
+        service.RecordCoinsFound(Coins.Of(30));
+
+        service.AbandonAttempt();
+
+        Assert.Equal(3, service.Lives.Value);
+        Assert.Equal(Coins.Zero, service.TotalCoins);
+    }
+
+    [Fact]
+    public void A_cheat_rewrites_the_save_shaped_state_and_is_still_validated()
+    {
+        // Cheats go through the snapshot rather than bare mutators, so ADR-0005 holds: there is still
+        // no SetLives or AddCoins for gameplay code to reach for.
+        var service = ServiceWithSkills();
+
+        service.ApplyCheat(snapshot => snapshot with { Bank = 500, Lives = 9 });
+
+        Assert.Equal(Coins.Of(500), service.TotalCoins);
+        Assert.Equal(9, service.Lives.Value);
+
+        // Still validated on the way back in: a negative bank is refused, state left alone.
+        Assert.Throws<ArgumentOutOfRangeException>(
+            () => service.ApplyCheat(snapshot => snapshot with { Bank = -1 }));
+        Assert.Equal(Coins.Of(500), service.TotalCoins);
+    }
+
     [Fact]
     public void Picking_up_a_coin_announces_the_new_total_so_the_hud_never_polls()
     {