feat: add action battle boss AI foundations

[RSamaium]

Summary

• add composable once, cooldown, phase, wait, and delayed-sequence behavior-tree helpers
• add server-side run/action, speed, point movement, hold, and teleport intents
• route serializable AI visual cues through a client registry that safely ignores unknown kinds
• document the public API and demonstrate a two-phase boss in sample-dev
• add a patch changeset and split the remaining Improve action-battle AI ergonomics for boss behaviors and server-driven visuals #309 roadmap into Expose advanced action-battle AI presets and options in Studio #334, Add tactical movement helpers for action-battle AI #335, Add configurable action-battle target selection and threat strategies #336, and Add action-battle summon and spawn intents through an extensible factory #337

Part of #309.

Validation

• pnpm build
• pnpm test -- --run — 153 files, 1,118 passed, 19 skipped
• pnpm test:types — 4 files, 22 tests, no type errors
• pnpm api:boundary
• focused Action Battle tests — 37 passed
• packed @rpgjs/action-battle, installed it in rpgjs/starter@v5, and completed a production build
• launched the starter on port 4179, verified HTTP 200, keyboard movement, no console/page/request failures, and reviewed a screenshot

The starter's missing @rpgjs/ui-css source-theme warning and large-chunk warning also occur with the currently published packages and are not regressions.