Add agent seam: bulk ops + majordomo tool wrappers (#19)

Bulk, natural-language-shaped service operations (ACL-enforced like every other
op, so agent tools inherit permissions for free):
- ops.go: Region + NamedRegion (nw/ne/sw/se corners, north/south/east/west and
  top/bottom/left/right halves, "all"; -y is north in the local frame).
  FillRegion hex-packs plops at 2×radius pitch (radius = #15's max(1.5·spacing,
  15cm)) clipped to the region, skipping any candidate that would sit entirely
  inside an existing active plop. ClearObject soft-removes all active plops in one
  UPDATE. DescribeGarden returns a structured summary (dims, objects+version,
  plantings with plant/effective-count/rough compass location).
- store/plantings.go: ListActivePlantingsForObject + ClearObjectPlantings.

Agent toolbox (internal/agent), deliberately isolated:
- doc.go (untagged) keeps the package in the default build; tools.go is behind
  the `majordomo` build tag and NOT in go.mod, so `go build/test ./...` and the
  server binary carry no majordomo/LLM deps. Built + tested locally against real
  majordomo (go test -tags majordomo ./internal/agent/).
- NewToolbox(svc, actorID) exposes list_gardens, describe_garden, create_object,
  move_object, place_planting, fill_region, clear_object as llm.DefineTool
  wrappers — thin typed adapters over the service, each running as the bound
  actor.

Tests: NamedRegion for all names + unknown→ErrInvalidInput; deterministic
hex-packing count (60×60 bed → 4 plops) + re-fill skips covered; rotated bed
fills the correct LOCAL corner; ClearObject; viewer→ErrForbidden on fill/clear
but can describe; and the DESIGN corner/half scenario (garlic NE, basil NW, beans
south) verified via DescribeGarden. A tagged demo drives the same scenario
through the toolbox (JSON args → tool → service) and confirms a viewer is refused.

GOWORK=off go build/vet/test ./internal/... green (majordomo-free).

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01JdQpdYYsTgtkJBxbcpAszi

internal/agent/doc.go

@@ -0,0 +1,18 @@
+// Package agent adapts pansy's service layer to majordomo tools so an agent can
+// drive a garden in natural language ("fill the NE corner with garlic, the NW
+// with basil, the south half with beans"). Each tool runs as a fixed actor and
+// therefore inherits pansy's ACL checks for free — a viewer's fill_region returns
+// ErrForbidden, exactly as the REST API would.
+//
+// Two deliberate separations keep the core server lean:
+//
+//   - cmd/pansy does NOT import this package, so the server binary carries no
+//     agent/LLM dependencies.
+//   - the tool wiring (tools.go) sits behind the `majordomo` build tag, so the
+//     default `go build ./...` / `go test ./...` compiles without the majordomo
+//     module. Build the agent tools with `-tags majordomo` once majordomo is a
+//     dependency (`go get gitea.stevedudenhoeffer.com/steve/majordomo`).
+//
+// The agent harness itself (model loop, chat surface) lives in the
+// majordomo/executus stack, outside this repo; this package is only the toolbox.
+package agent