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/store/plantings.go

@@ -56,6 +56,53 @@ func (d *DB) ListActivePlantingsForGarden(ctx context.Context, gardenID int64) (
 	return plantings, nil
 }
 
+// ListActivePlantingsForObject returns an object's currently-planted plops
+// (removed_at IS NULL). Always a non-nil slice. Used by FillRegion to avoid
+// stacking new plops inside existing ones.
+func (d *DB) ListActivePlantingsForObject(ctx context.Context, objectID int64) ([]domain.Planting, error) {
+	rows, err := d.sql.QueryContext(ctx,
+		`SELECT `+plantingColumns+` FROM plantings WHERE object_id = ? AND removed_at IS NULL ORDER BY id`,
+		objectID,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("store: list object plantings: %w", err)
+	}
+	defer rows.Close()
+
+	plantings := []domain.Planting{}
+	for rows.Next() {
+		p, err := scanPlanting(rows)
+		if err != nil {
+			return nil, fmt.Errorf("store: scan planting: %w", err)
+		}
+		plantings = append(plantings, *p)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, fmt.Errorf("store: iterate plantings: %w", err)
+	}
+	return plantings, nil
+}
+
+// ClearObjectPlantings soft-removes every active plop in an object in one UPDATE
+// (sets removed_at=date, bumps version) and returns how many rows it affected.
+func (d *DB) ClearObjectPlantings(ctx context.Context, objectID int64, date string) (int, error) {
+	res, err := d.sql.ExecContext(ctx,
+		`UPDATE plantings
+		    SET removed_at = ?, version = version + 1,
+		        updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
+		  WHERE object_id = ? AND removed_at IS NULL`,
+		date, objectID,
+	)
+	if err != nil {
+		return 0, fmt.Errorf("store: clear object plantings: %w", err)
+	}
+	n, err := res.RowsAffected()
+	if err != nil {
+		return 0, fmt.Errorf("store: clear plantings rows: %w", err)
+	}
+	return int(n), nil
+}
+
 // GetPlanting returns the planting with the given id, or domain.ErrNotFound.
 func (d *DB) GetPlanting(ctx context.Context, id int64) (*domain.Planting, error) {
 	p, err := scanPlanting(d.sql.QueryRowContext(ctx,