docs: define initial quest board stories

AGENTS.md

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+# Spigot Quest Board Agent Guide
+
+## Project
+
+Spigot Quest Board is a Java 25 plugin for Purpur 26.2. It provides shared physical quest boards where players escrow rewards, deliver requested block items, and claim delivered or returned items.
+
+## Canonical knowledge
+
+- `knowledge/` is the canonical OKF v0.1 knowledge bundle.
+- Read `knowledge/index.md` and the relevant documents in `knowledge/user-stories/` before changing behavior.
+- Every feature or behavior change requires an approved user story with task-list acceptance criteria.
+- Preserve unknown YAML frontmatter fields when editing knowledge documents.
+- Keep `knowledge/index.md`, `knowledge/log.md`, and `knowledge/user-stories/index.md` current.
+
+## Development
+
+- Compile against the Purpur API version declared in `build.gradle.kts`.
+- Use Java 25 and enable strict compiler linting.
+- Prefer small, server-independent domain objects and services that can be unit tested.
+- Use test-driven development where practical: add a failing test, implement the minimum behavior, then refactor.
+- Treat escrow, completion, cancellation, expiry, and claiming as atomic state transitions. Never duplicate or silently discard player items.
+- Key players by UUID, not display name.
+- Persist board, quest, escrow, and claim state safely across restarts using atomic file replacement where supported.
+- Use UTC and RFC 3339 timestamps for persisted or documented date-times.
+- Keep player-facing command autocomplete permission-aware and context-sensitive.
+- Use Purpur's supported Paper dialog API for native dialog interfaces.
+
+## Verification
+
+Run before completing a story:
+
+```bash
+./gradlew clean check jar
+```
+
+Mark acceptance criteria complete only after implementation and verification.
+
+## Git
+
+Use conventional commits in the form `type(scope): description`, with summaries under 72 characters.