feat(quests): add issuer quest cancellation

knowledge/log.md

@@ -54,3 +54,10 @@ description: Chronological record of material decisions affecting Spigot Quest B
 - Completion serializes state transitions, holds delivered blocks in durable issuer claims, and grants exact escrowed rewards with owner-protected overflow drops.
 - Added durable online and next-login issuer notifications and rollback before persistence succeeds.
 - Verified 49 tests and the plugin JAR with `./gradlew clean check jar`.
+
+## 2026-09-05 — Issuer quest cancellation
+
+- Added issuer-only board actions and `/quests cancel <quest>` with ownership-filtered autocomplete.
+- Cancellation atomically moves exact reward escrow into an issuer claim without directly changing inventory.
+- Serialized cancellation against completion and retained active state when persistence fails.
+- Verified 58 tests and the plugin JAR with `./gradlew clean check jar`.

knowledge/user-stories/us-006-cancel-an-owned-quest.md

@@ -2,7 +2,7 @@
 type: User Story
 title: "US-006: Cancel an owned quest"
 description: Let an issuer cancel an active quest and reclaim its escrowed reward safely.
-status: backlog
+status: done
 ---
 
 # US-006: Cancel an owned quest
@@ -11,15 +11,15 @@ As a **quest issuer**, I want to cancel my active quest so that I can reclaim th
 
 ## Acceptance criteria
 
-- [ ] An issuer can cancel their own active quest through any registered board.
-- [ ] A player cannot cancel a quest issued by another player.
-- [ ] Completed, cancelled, and expired quests cannot be cancelled.
-- [ ] Cancellation removes the quest from active listings and converts its exact escrowed reward into a claim for the issuer.
-- [ ] The reward is not inserted directly into the issuer's inventory during cancellation.
-- [ ] When player commands are enabled, `/quests cancel <quest>` provides equivalent behavior and only autocompletes the player's cancellable quest identifiers.
-- [ ] Cancellation and simultaneous completion are serialized so items cannot be duplicated or lost.
-- [ ] Persistence failure leaves the quest active and its reward escrowed.
-- [ ] Automated tests verify ownership, state validation, claim creation, autocomplete, rollback, and completion races.
+- [x] An issuer can cancel their own active quest through any registered board.
+- [x] A player cannot cancel a quest issued by another player.
+- [x] Completed, cancelled, and expired quests cannot be cancelled.
+- [x] Cancellation removes the quest from active listings and converts its exact escrowed reward into a claim for the issuer.
+- [x] The reward is not inserted directly into the issuer's inventory during cancellation.
+- [x] When player commands are enabled, `/quests cancel <quest>` provides equivalent behavior and only autocompletes the player's cancellable quest identifiers.
+- [x] Cancellation and simultaneous completion are serialized so items cannot be duplicated or lost.
+- [x] Persistence failure leaves the quest active and its reward escrowed.
+- [x] Automated tests verify ownership, state validation, claim creation, autocomplete, rollback, and completion races.
 
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