Implement the transactional gameplay event and action foundation

[zoeyrose]

Outcome

Give every gameplay mutation one typed, deterministic preflight/commit/cancel path and one bounded event publication model.

Scope and invariants

• Define immutable action requests/context, captured stable identities, authorization, costs, target/shape data, and source attribution.
• Preflight is pure and repeatable; commit is atomic against one simulation owner; cancellation and retry semantics are explicit.
• Order nested events deterministically, bound recursion/fan-out, prevent accidental reentrancy, and attach idempotency keys where external retries occur.
• Separate domain events, durable metrics, client projections, and operational telemetry; consumers cannot mutate the transaction in callbacks.
• Provide common inventory/currency/state effect primitives with rollback-safe error handling.

Acceptance criteria

• Property tests prove rejected/failed actions publish no success event and leave no partial effects.
• Nested/recursive triggers hit typed bounds without corrupting the tick.
• Timed actions Replace post-action cooldowns with server-authoritative wind-ups and timed animations #25, activities Generalize tool-based harvesting and crafting from Sam's saw quest #35, combat Combat disciplines: build the action framework and Sweeping Cleave slice #17, quests Implement the native Go quest engine #43, and triggers Implement generic map/object triggers and authored action graphs #54 reuse this foundation; architecture tests reject private transaction engines.
• Replay fixtures produce identical ordered event streams and state digests.
• Scenario failures identify action ID, phase, and stable entities without exposing secrets or hidden player data.

Dependencies and parallelization

Depends on #32 and #37; persistence/event adapters may be stubbed. Domain systems can design typed requests in parallel once the contract is approved.

Independent implementation

New code and tests are MIT-licensed independent work. Preserve public behavior and issue-level design choices, but do not copy or mechanically translate GPL server/Python implementation or tests. Mixed-license content remains external data with its own notices.