feat(commands): add permission-aware tab completion

design/user-stories/index.md

@@ -13,3 +13,4 @@ description: Catalog of user stories for the Spigot Creeper Fear plugin.
 - [US-005: Administer player progression](us-005-administer-player-progression.md)
 - [US-006: Configure aura progression](us-006-configure-aura-progression.md)
 - [US-007: Build and release the plugin](us-007-build-and-release-plugin.md)
+- [US-008: Autocomplete commands](us-008-autocomplete-commands.md)

design/user-stories/us-008-autocomplete-commands.md

@@ -0,0 +1,31 @@
+---
+type: User Story
+title: "US-008: Autocomplete commands"
+description: Help players and administrators discover valid Creeper Aura command arguments with permission-aware tab completion.
+status: done
+---
+
+# US-008: Autocomplete commands
+
+As a **command sender**, I want Creeper Aura commands to offer relevant tab completions so that I can enter valid commands quickly and accurately.
+
+## Acceptance criteria
+
+- [x] `/creeperaura` suggests only subcommands allowed by the sender's permissions.
+- [x] `progress`, `set`, `add`, and `rank` suggest matching online player names where appropriate.
+- [x] `rank` suggests `locked`, `I`, `II`, `III`, `IV`, `V`, and `VI`.
+- [x] `threshold` suggests configurable ranks `I` through `VI`.
+- [x] Suggestions are filtered case-insensitively by the current input.
+- [x] Unauthorized administrative subcommands and arguments are not suggested.
+- [x] Completion works for both players and the server console.
+- [x] Automated tests cover completion behavior.
+- [x] Command metadata and project documentation describe autocomplete support.
+
+Offline stored players remain valid command targets but are not suggested, avoiding synchronous database access during completion.
+
+## Related
+
+- [Check personal progress](us-004-check-personal-progress.md)
+- [Administer player progression](us-005-administer-player-progression.md)
+- [Configure aura progression](us-006-configure-aura-progression.md)
+- [User-story catalog](index.md)